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JEE physics MCQ

Wave Optics · CBSE STD 12 Science (CBSE - English Medium). 272 questions.

Questions · Page 4 of 6

MCQ

MCQ 1511 Mark
Through which character we can distinguish the light waves from sound waves
  • A
    Interference
  • B
    Refraction
  • ✓
    Polarisation
  • D
    Reflection
Answer
Correct option: C.
Polarisation
Polarisation is not shown by sound waves.
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MCQ 1521 Mark
Pick out the longest wavelength from the following types of radiations
  • A
    Blue light
  • B
    $\gamma$-rays
  • C
    $X$-rays
  • ✓
    Red light
Answer
Correct option: D.
Red light
$\lambda_{\operatorname{Re} d}>\lambda_{\text {Blue }}>\lambda_{X-\text { ray }}>\lambda_\gamma$
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MCQ 1531 Mark
Two waves of intensity $l$ undergo Interference. The maximum intensity obtained is
  • A
    $1 / 2$
  • B
    $l$
  • C
    $21$
  • ✓
    $4 l$
Answer
Correct option: D.
$4 l$
$4 l$
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MCQ 1541 Mark
If two light waves having same frequency have intensity ratio $4: 1$ and they interfere, the ratio of maximum to minimum intensity in the pattern will be
  • ✓
    $9: 1$
  • B
    $3: 1$
  • C
    $25: 9$
  • D
    $16: 25$
Answer
Correct option: A.
$9: 1$
$\frac{I_{\max }}{I_{\min }}=\left(\frac{\sqrt{\frac{I_1}{I_2}}+1}{\sqrt{\frac{I_1}{I_2}}-1}\right)^2=\left(\frac{\sqrt{\frac{4}{1}}+1}{\sqrt{\frac{4}{1}}-1}\right)^2=\frac{9}{1}$
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MCQ 1551 Mark
The region of the atmosphere above troposphere is known as
  • A
    Lithosphere
  • B
    Uppersphere
  • C
    lonosphere
  • ✓
    Stratosphere
Answer
Correct option: D.
Stratosphere
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MCQ 1561 Mark
Heat radiations propagate with the speed of
  • A
    $\alpha$-rays
  • B
    $\beta$-rays
  • ✓
    light waves
  • D
    Sound waves
Answer
Correct option: C.
light waves
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MCQ 1571 Mark
Radio wave diffract around building although light waves do not. The reason is that radio waves
  • A
    Travel with speed larger than $c$
  • ✓
    Have much larger wavelength than light
  • C
    Carry news
  • D
    Are not electromagnetic waves
Answer
Correct option: B.
Have much larger wavelength than light
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MCQ 1581 Mark
In case of linearly polarized light, the magnitude of the electric field vector:
  • A
    Does not change with time
  • ✓
    Varies periodically with time
  • C
    Increases and decreases linearly with time
  • D
    Is parallel to the direction of propagation
Answer
Correct option: B.
Varies periodically with time
The magnitude of electric field vector varies periodically with time because it is the form of electromagnetic wave.
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MCQ 1591 Mark
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is
  • A
    Polarised
  • B
    Of longer wavelength
  • ✓
    Of shorter wavelength
  • D
    Of high intensity
Answer
Correct option: C.
Of shorter wavelength
When a beam of light is used to determine the position of an object, the maximum accuracy is achieved if the light is of shorter wavelength, because$\text { Accuracy } \propto \frac{1}{\text { Wavelength }}$
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MCQ 1601 Mark
What is the path difference of destructive interference
  • A
    $n \lambda$
  • B
    $n(\lambda+1)$
  • C
    $\frac{(n+1) \lambda}{2}$
  • ✓
    $\frac{(2 n+1) \lambda}{2}$
Answer
Correct option: D.
$\frac{(2 n+1) \lambda}{2}$
For destructive interference path difference is odd multiple of $\frac{\lambda}{2}$.
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MCQ 1611 Mark
According to Maxwell's hypothesis, a changing electric field gives rise to
  • A
    An e.m.f.
  • B
    Electric current
  • ✓
    Magnetic field
  • D
    Pressure radiant
Answer
Correct option: C.
Magnetic field
According to the Maxwell's EM theory, the EM waves propagation contains electric and magnetic field vibration in mutually perpendicular direction. Thus the changing of electric field give rise to magnetic field.
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MCQ 1621 Mark
If a star is moving towards the earth, then the lines are shifted towards
  • A
    Red
  • B
    Infrared
  • ✓
    Blue
  • D
    Green
Answer
Correct option: C.
Blue
When the source and observer approach each other, apparent frequency increases and hence wavelength decreases.
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MCQ 1631 Mark
The maximum distance upto which $TV$ transmission from a $TV$ tower of height $h$ can be received is proportional to
  • ✓
    $h^{1 / 2}$
  • B
    $h$
  • C
    $h^3$
  • D
    $h^2$
Answer
Correct option: A.
$h^{1 / 2}$
$h^{1 / 2}$
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MCQ 1641 Mark
In Young's double slit experiment, if monochromatic light is replaced by white light
  • ✓
    (a) All bright fringes become white
  • B
    (b) All bright fringes have colours between violet and red
  • C
    (c) Only the central fringe is white, all other fringes are coloured
  • D
    (d) No fringes are observed
Answer
Correct option: A.
(a) All bright fringes become white
(a) In conventional light source, light comes from a large number of independent atoms, each atom emitting light for about 10 . sec i.e. light emitted by an atom is essentially a pulse lasting for only 10 sec. Light coming out from two slits will have a fixed phase relationship only for $10 sec$. Hence any interference pattern formed on the screen would last only for $10 sec$, and then the pattern will change. The human eye can notice intensity changes which last at least for a tenth of a second and hence we will not be able to see any interference pattern. In stead due to rapid changes in the pattern, we will only observe a uniform intensity over the screen.
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MCQ 1651 Mark
In Young's double slit experiment, if monochromatic light is replaced by white light

Image

  • A
    (a) All bright fringes become white
  • B
    (b) All bright fringes have colours between violet and red
  • C
    (c) Only the central fringe is white, all other fringes are coloured
  • D
    (d) No fringes are observed
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MCQ 1661 Mark
When an unpolarized light of intensity $I_0$ is incident on a polarizing sheet, the intensity of the light which does not get transmitted is
  • A
    Zero
  • B
    $I_0$
  • ✓
    $\frac{1}{2} I_0$
  • D
    $\frac{1}{4} I_0$
Answer
Correct option: C.
$\frac{1}{2} I_0$
If an unpolarised light is converted into plane polarised light by passing through a polaroid, it's intensity becomes half.
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MCQ 1671 Mark
The intensity of gamma radiation from a given source is $l$. On passing through $36 mm$ of lead, it is reduced to $\frac{I}{8}$. The thickness of lead which will reduce the intensity to $\frac{I}{2}$ will be
  • A
    $18\ mm$
  • ✓
    $12\ mm$
  • C
    $6\ mm$
  • D
    $9\ mm$
Answer
Correct option: B.
$12\ mm$
$ I=I e^{-\mu x} \Rightarrow x=\frac{1}{\mu} \log _e \frac{I}{I^{\prime}} \quad$ (where $I=$ original intensity, $I^{\prime}$ $=$ changed intensity)
$36=\frac{1}{\mu} \log _e \frac{I}{I / 8}=\frac{3}{\mu} \log _e 2 $
$x=\frac{1}{\mu} \log _e \frac{I}{I / 2}=\frac{1}{\mu} \log _e 2$
From equation (i) and (ii), $x=12 mm$.
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MCQ 1681 Mark
If $I_0$ is the intensity of the principal maximum in the single slit diffraction pattern, then what will be its intensity when the slit width is doubled
  • A
    $I_0$
  • B
    $\frac{ I _0}{2}$
  • C
    $2 I_0$
  • ✓
    $4 I_0$
Answer
Correct option: D.
$4 I_0$
$4 I_0$
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MCQ 1691 Mark
An electromagnetic wave of frequency $v=3.0 MHz$ passes from vacuum into a dielectric medium with permitivity $\varepsilon=4.0$. Then
  • A
    Wavelength is doubled and the frequency remains unchanged
  • B
    Wavelength is doubled and frequency becomes half
  • ✓
    Wavelength is halved and frequency remains unchanged
  • D
    Wavelength and frequency both remain unchanged
Answer
Correct option: C.
Wavelength is halved and frequency remains unchanged
Wavelength is halved and frequency remains unchanged
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MCQ 1701 Mark
The maximum number of possible interference maxima for slitseparation equal to twice the wavelength in Young's double-slit experiment is
  • A
    Infinite
  • B
    Five
  • ✓
    Three
  • D
    Zero
Answer
Correct option: C.
Three
The interference fringes for two slits are hyperbolic.
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MCQ 1711 Mark
To demonstrate the phenomenon of interference, we require two sources which emit radiation
  • ✓
    Of the same frequency and having a define phase relationship
  • B
    Of nearly the same frequency
  • C
    Of the same frequency
  • D
    Of different wavelengths
Answer
Correct option: A.
Of the same frequency and having a define phase relationship
For interference frequency must be same and phase difference must be constant.
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MCQ 1721 Mark
Which of the following radiations has the least wavelength
  • ✓
    $\gamma$-rays
  • B
    $\beta$-rays
  • C
    $\alpha$-rays
  • D
    $X$-rays
Answer
Correct option: A.
$\gamma$-rays
$\lambda_{\gamma \text {-rays }}<\lambda_{x-\text { rays }}<\lambda_{\alpha}-\text { rays }<\lambda_{\beta-\text { rays }}$.
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MCQ 1731 Mark
Which of the following are not electromagnetic waves
  • A
    Cosmic rays
  • B
    Gamma rays
  • ✓
    $\beta$-rays
  • D
    $X$-rays
Answer
Correct option: C.
$\beta$-rays
$\beta$-rays are beams of fast electrons.
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MCQ 1741 Mark
Electromagnetic waves are transverse in nature is evident by
  • ✓
    Polarization
  • B
    Interference
  • C
    Reflection
  • D
    Diffraction
Answer
Correct option: A.
Polarization
Polarization is shown by only transverse waves.
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MCQ 1751 Mark
What causes changes in the colours of the soap or oil films for the given beam of light
  • A
    Angle of incidence
  • B
    Angle of reflection
  • ✓
    Thickness of film
  • D
    None of these
Answer
Correct option: C.
Thickness of film
For viewing interference in oil films or soap bubble, thickness of film is of the order of wavelength of light.
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MCQ 1761 Mark
Which of the following is not a property of light
  • ✓
    It requires a material medium for propagation
  • B
    It can travel through vacuum
  • C
    It involves transportation of energy
  • D
    It has finite speed
Answer
Correct option: A.
It requires a material medium for propagation
light is electromagnetic in nature it does not require any material medium for its propagation.
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MCQ 1771 Mark
Refractive index of material is equal to tangent of polarising angle. It is called
  • ✓
    Brewster's law
  • B
    Lambert's law
  • C
    Malus's law
  • D
    Bragg's law
Answer
Correct option: A.
Brewster's law
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MCQ 1781 Mark
For skywave propagation of a $10 MHz$ signal, what should be the minimum electron density in ionosphere
  • ✓
    $\sim 1.2 \times 10^{12} m ^{-3}$
  • B
    $\sim 10^6 m ^{-3}$
  • C
    $\sim 10^{14} m ^{-3}$
  • D
    $\sim 10^{22} m ^{-3}$
Answer
Correct option: A.
$\sim 1.2 \times 10^{12} m ^{-3}$
$\sim 1.2 \times 10^{12} m ^{-3}$
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MCQ 1791 Mark
Huygen wave theory allows us to know
  • A
    The wavelength of the wave
  • B
    The velocity of the wave
  • C
    The amplitude of the wave
  • ✓
    The propagation of wave fronts
Answer
Correct option: D.
The propagation of wave fronts
Huygen's theory explains propagation of wave front.
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MCQ 1801 Mark
Which scientist experimentally proved the existence of electromagnetic waves
  • A
    Sir J.C. Bose
  • B
    Maxwell
  • ✓
    Marconi
  • D
    Hertz
Answer
Correct option: C.
Marconi
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MCQ 1811 Mark
If an interference pattern have maximum and minimum intensities in $36: 1$ ratio then what will be the ratio of amplitudes
  • A
    $5: 7$
  • B
    $7: 4$
  • C
    $4: 7$
  • ✓
    $7: 5$
Answer
Correct option: D.
$7: 5$
$\frac{I_{\max }}{I_{\min }}=\left(\frac{\frac{a_1}{a_2}+1}{\frac{a_1}{a_2}-1}\right)^2 $
$\Rightarrow \frac{a_1+a_2}{a_1-a_2}=6 $
$\frac{a_2}{a_1}=7: 5$
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MCQ 1821 Mark
Which of the following waves have the maximum wavelength
  • A
    $X$-rays
  • B
    I.R. rays
  • C
    UV rays
  • ✓
    Radio waves
Answer
Correct option: D.
Radio waves
$\lambda_{\text {Radiowaves }}>\lambda_{U V \text { rays }}>\lambda_{J \text { Rays }}>\lambda_{X \text {-rays }}$
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MCQ 1831 Mark
What is ozone hole
  • A
    Hole in the ozone layer
  • B
    Formation of ozone layer
  • C
    Thinning of ozone layer in troposphere
  • ✓
    Reduction in ozone thickness in stratosphere
Answer
Correct option: D.
Reduction in ozone thickness in stratosphere
Ozone hole is depletion of ozone layer in stratosphere because of gases like CFC'S etc.
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MCQ 1841 Mark
Which radiation in sunlight, causes heating effect
  • A
    Ultraviolet
  • ✓
    Infrared
  • C
    Visible light
  • D
    All of these
Answer
Correct option: B.
Infrared
Infrared causes heating effect.
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MCQ 1851 Mark
If the ratio of amplitude of two waves is $4: 3$, then the ratio of maximum and minimum intensity is
  • A
    $16: 18$
  • B
    $18: 16$
  • ✓
    $49: 1$
  • D
    $94: 1$
Answer
Correct option: C.
$49: 1$
$\frac{I_{\max }}{I_{\min }}=\left(\frac{\frac{a_1}{a_2}+1}{\frac{a_1}{a_2}-1}\right)^2=\left(\frac{\frac{4}{3}+1}{\frac{4}{3}-1}\right)^2=\frac{49}{1}$
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MCQ 1861 Mark
Soap bubble appears coloured due to the phenomenon of
  • ✓
    Interference
  • B
    Diffraction
  • C
    Dispersion
  • D
    Reflection
Answer
Correct option: A.
Interference
Phenomenon of interference of light takes place.
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MCQ 1871 Mark
By a monochromatic wave, we mean
  • A
    A single ray
  • B
    A single ray of a single colour
  • ✓
    Wave having a single wavelength
  • D
    Many rays of a single colour
Answer
Correct option: C.
Wave having a single wavelength
Monochromatic wave means of single wavelength not the single colour.
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MCQ 1881 Mark
Two waves having intensity in the ratio $25: 4$ produce interference. The ratio of the maximum to the minimum intensity is
  • A
    $5: 2$
  • B
    $7: 3$
  • ✓
    $49: 9$
  • D
    $9: 49$
Answer
Correct option: C.
$49: 9$
$\frac{I_{\max }}{I_{\min }}=\left(\frac{\sqrt{\frac{I_1}{I_2}}+1}{\sqrt{\frac{I_1}{I_2}}-1}\right)^2=\left(\frac{\sqrt{\frac{25}{4}+1}}{\sqrt{\frac{25}{4}}-1}\right)^2=\frac{49}{9}$
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MCQ 1891 Mark
Two light sources are said to be coherent if they are obtained from
  • A
    Two independent point sources emitting light of the same wavelength
  • ✓
    A single point source
  • C
    A wide source
  • D
    Two ordinary bulbs emitting light of different wavelengths
Answer
Correct option: B.
A single point source
When two sources are obtained from a single source, the wavefront is divided into two parts. These two wavefronts acts as if they emanated from two sources having a fixed phase relationship.
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MCQ 1901 Mark
Evidence for the wave nature of light cannot be obtained from
  • ✓
    Reflection
  • B
    Doppler effect
  • C
    Interference
  • D
    Diffraction
Answer
Correct option: A.
Reflection
Reflection phenomenon is shown by both particle and wave nature of light.
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MCQ 1911 Mark
Two sources of waves are called coherent if
  • A
    Both have the same amplitude of vibrations
  • B
    Both produce waves of the same wavelength
  • ✓
    Both produce waves of the same wavelength having constant phase difference
  • D
    Both produce waves having the same velocity
Answer
Correct option: C.
Both produce waves of the same wavelength having constant phase difference
Two coherent source must have a constant phase difference otherwise they can not produce interference.
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MCQ 1921 Mark
light appears to travel in straight lines since
  • A
    It is not absorbed by the atmosphere
  • B
    It is reflected by the atmosphere
  • ✓
    Its wavelength is very small
  • D
    Its velocity is very large
Answer
Correct option: C.
Its wavelength is very small
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MCQ 1931 Mark
Two coherent monochromatic light beams of intensities $I$ and $4 l$ are superposed. The maximum and minimum possible intensities in the resulting beam are
  • A
    $5 l$ and $l$
  • B
    $5 l$ and $3 l$
  • ✓
    $9 l$ and $l$
  • D
    $9 l$ and $3 l$
Answer
Correct option: C.
$9 l$ and $l$
$I_{\max }=\left(\sqrt{I_1}+\sqrt{I_2}\right)^2=(\sqrt{I}+\sqrt{4 I})^2=9 I $
$I_{\min }=\left(\sqrt{I_1}-\sqrt{I_2}\right)^2=(\sqrt{I}-\sqrt{4 I})^2=I$
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MCQ 1941 Mark
The phenomenon of interference is shown by
  • A
    Longitudinal mechanical waves only
  • B
    Transverse mechanical waves only
  • C
    Electromagnetic waves only
  • ✓
    All the above types of waves
Answer
Correct option: D.
All the above types of waves
Interference is shown by transverse as well as mechanical waves.
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MCQ 1951 Mark
By Huygen's wave theory of light, we cannot explain the phenomenon of
  • A
    Interference
  • B
    Diffraction
  • ✓
    Photoelectric effect
  • D
    Polarisation
Answer
Correct option: C.
Photoelectric effect
Huygen's wave theory fails to explain the particle nature of light (i.e. photoelectric effect)
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MCQ 1961 Mark
According to corpuscular theory of light, the different colours of light are due to
  • A
    Different electromagnetic waves
  • B
    Different force of attraction among the corpuscles
  • ✓
    Different size of the corpuscles
  • D
    None of the above
Answer
Correct option: C.
Different size of the corpuscles
According to Corpuscular theory different colour of light are due to different size of Corpuscules.
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MCQ 1971 Mark
By corpuscular theory of light, the phenomenon which can be explained is
  • ✓
    Refraction
  • B
    Interference
  • C
    Diffraction
  • D
    Polarisation
Answer
Correct option: A.
Refraction
Corpuscular theory explains refraction of light.
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MCQ 1981 Mark
In the visible region of the spectrum the rotation of the place of polarization is given by $\theta=a+\frac{b}{\lambda^2}$. The optical rotation produced by a particular material is found to be $30^{\circ}$ per $mm$ at $\lambda=5000 \mathring A$ and $50^{\circ}$ per $mm$ at $\lambda=4000 \mathring A$. The value of constant $a$ will be
  • A
    $+\frac{50^{\circ}}{9}$ per $mm$
  • ✓
    $-\frac{50^{\circ}}{9}$ per $mm$
  • C
    $+\frac{9^{\circ}}{50}$ per $mm$
  • D
    $-\frac{9^{\circ}}{50}$ per $mm$
Answer
Correct option: B.
$-\frac{50^{\circ}}{9}$ per $mm$
$\theta=a+\frac{b}{\lambda^2}$
$30=a+\frac{b}{(5000)^2} \text { and } 50=a+\frac{b}{(4000)^2}$
Solving for a, we get $a=-\frac{50^{\circ}}{9}$ per $mm$
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MCQ 1991 Mark
Unpolarized light of intensity $32 Wm$ passes through three polarizers such that transmission axes of the first and second polarizer makes and angle $30^{\circ}$ with each other and the transmission axis of the last polarizer is crossed with that of the first. The intensity of final emerging light will be
  • A
    (a) $32 Wm$
  • B
    (b) $3 Wm$
  • C
    (c) $8 Wm$
  • D
    (d) $4 Wm$
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MCQ 2001 Mark
Unpolarized light falls on two polarizing sheets placed one on top of the other. What must be the angle between the characteristic directions of the sheets if the intensity of the final transmitted light is one-third the maximum intensity of the first transmitted beam
  • A
    $75^{\circ}$
  • ✓
    $55^{\circ}$
  • C
    $35^{\circ}$
  • D
    $15^{\circ}$
Answer
Correct option: B.
$55^{\circ}$
$I=\frac{I}{2} \cos ^2 \theta=\frac{I}{6}$ or $\cos \theta=\frac{1}{\sqrt{3}} $
$\therefore \theta=55^{\circ}$
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