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Light Waves Physics - Light Waves

Jharkhand Board (JAC) - STD 12 Science - Physics (Jharkhand - English Medium). 72 questions in this chapter.

Question types

Light Waves question types

72 questions across 6 question groups — pick any mix to generate a Physics paper with step-by-step answer keys.

72
Questions
6
Question groups
5
Question types
Sample Questions

Light Waves questions

One sample from each question group in this chapter. Select any group above to see the full set with answer keys.

Q 1M.C.Q (1 Marks)1 Mark
Two coherent sources of different intensities send waves which interfere. The ratio of maximum intensity to the minimum intensity is 25. The intensities of the sources are in the ratio:
  • A
    25 : 1
  • B
    5 : 1
  • ✓
    9 : 4
  • D
    625 : 1

Answer: C.

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Q 2M.C.Q (1 Marks)1 Mark
The inverse square law of intensity $\Big(\text{i.e., the intensity}\propto\frac{1}{\text{r}^2}\Big)$ is valid for a:
  • ✓
    Point source.
  • B
    Line source.
  • C
    Plane source.
  • D
    Cylindrical source.

Answer: A.

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Q 3M.C.Q (1 Marks)1 Mark
The slits in a Young's double slit experiment have equal width and the source is placed symmetrically with respect to the slits. The intensity at the central fringe is $I_0$. If one of the slits is closed, the intensity at this point will be:
  • A
    $\text{I}_0$
  • ✓
    $\frac{\text{I}_0}{4}$
  • C
    $\frac{\text{I}_0}{2}$
  • D
    $4\text{I}_0$

Answer: B.

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Q 4M.C.Q (1 Marks)1 Mark
The equation of a light wave is written as $\text{y}=\text{A}\ \sin(\kappa\text{x}-\omega\text{t}).$ Here, y represents:
  • A
    Displacement of either particles.
  • B
    Pressure in the medium.
  • C
    Density of the medium.
  • ✓
    Electric field.

Answer: D.

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Q 61 Marks Question1 Mark
Plane microwaves are incident on a long slit having a width of 5.0cm. Calculate the wavelength of the microwaves if the first diffraction minimum is formed at $\theta=30^\circ.$
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Q 71 Marks Question1 Mark
Find the thickness of a plate which will produce a change in optical path equal to half the wavelength $\lambda$ of the light passing through it normally. The refractive index of the plate is $\mu$.
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Q 81 Marks Question1 Mark
Consider the situation of the previous problem. If the mirror reflects only 64% of the light energy falling on it, what will be the ratio of the maximum to the minimum intensity in the interference pattern observed on the screen?
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Q 92 Marks Questions2 Marks
White light is used in a Young's double slit experiment. Find the minimum order of the violet fringe $(\lambda=400\text{nm}),$ which overlaps with a red fringe $(\lambda=700\text{nm}).$
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Q 102 Marks Questions2 Marks
Is it necessary to have two waves of equal intensity to study interference pattern? Will there be an effect on clarity if the waves have unequal intensity?
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Q 112 Marks Questions2 Marks
A source emitting light of wavelengths 480nm and 600nm is used in. a double slit interference experiment. The separation between the slits is 0.25mm and the interference is observed on a screen placed at 150cm from the slits. Find the linear separation between the first maximum (next to the central maximum) corresponding to the two wavelengths.
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Q 122 Marks Questions2 Marks
The linewidth of a bright fringe is sometimes defined as the separation between the points on the two sides of the central line where the intensity falls to half the maximum. Find the linewidth of a bright fringe in a Young's double slit experiment in terms of $\lambda$, d and D where the symbols have their usual meanings.
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Q 132 Marks Questions2 Marks
A parallel beam of light of wavelength 560nm falls on a thin film of oil (refractive index = 1.4). What should be the minimum thickness of the film so that it strongly reflects the light?
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Q 143 Marks Question3 Marks
Is the colour of 620nm light and 780nm light same? Is the colour of 620nm light and 621nm light same? How many colours are there in white light?
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Q 163 Marks Question3 Marks
Suppose white light falls on a double slit but one slit is covered by a violet filter (allowing $\lambda=400\text{nm}$). Describe the nature of the fringe pattern observed.
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Q 173 Marks Question3 Marks
If the separation between the slits in a Young's double slit experiment is increased, what happens to the fringe-width? If the separation is increased too much, will the fringe pattern remain detectable?
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Q 183 Marks Question3 Marks
The index of refraction of fused quartz is 1.472 for light of wavelength 400nm and is 1.452 for light of wavelength 760nm. Find the speeds of light of these wavelengths in fused quartz.
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Q 195 Marks Questions5 Marks
A parallel beam of white light is incident normally on a water film $1.0 \times 10^{-4}cm$ thick. Find the wavelength in the visible range (400nm - 700nm) which are strongly transmitted by the film. Refractive index of water = 1.33.
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Q 205 Marks Questions5 Marks
A thin paper of thickness 0.02mm having a refractive index 1.45 is pasted across one of the slits in a Young's double slit experiment. The paper transmits $\frac{4}{9}$ of the light energy falling on it.
  1. Find the ratio of the maximum intensity to the minimum intensity in the fringe pattern.
  2. How many fringes will cross through the centre if an identical paper piece is pasted on the other slit also? The wavelength of the light used is 600nm.
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Q 215 Marks Questions5 Marks
A glass surface is coated by an oil film of uniform thickness $1.00 \times 10^{-4}cm$. The index of refraction of the oil is 1.25 and that of the glass is 1.50. Find the wavelengths of light in the visible region (400nm - 750nm) which are completely transmitted by the oil film under normal incidence.
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Q 225 Marks Questions5 Marks
In a Young's double slit experiment using monochromatic light, the fringe pattern shifts by a certain distance on the screen when a mica sheet of refractive index 1.6 and thickness 1.964 micron $(1$ micron $= 10^{-6}m)$ is introduced in the path of one of the interfering waves. The mica sheet is then removed and the distance between the screen and the slits is doubled. It is found that the distance between the successive maxima now is the same as the observed fringe-shift upon the introduction of the mica sheet. Calculate the wavelength of the monochromatic light used in the experiment.
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Q 235 Marks Questions5 Marks
The wavelength of sodium light in air is 589nm.
  1. Find its frequency in air.
  2. Find its wavelength in water (refractive index = 1.33).
  3. Find its frequency in water.
  4. Find its speed in water.
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Q 24Case study (4 Marks)4 Marks
TV signals broadcast by Delhi studio cannot be directly received at Patna which is about 1000km away. But the same signal goes some 36000km away to a satellite, gets reflected and is then received at Patna. Explain.
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Q 25Case study (4 Marks)4 Marks
Why don't we have interference when two candles are placed close to each other and the intensity is seen at a distant screen? What happens if the candles are replaced by laser sources?
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