A parallel beam of light of wavelength 500 nm falls on a narrow slit and the resulting diffraction pattern is observed on a screen 1 m away. It is observed that the first minimum is at a distance of 2.5 mm from the centre of the screen. Find the width of the slit.
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2 Marks Questions
64 Q→023 Marks Question
55 Q→031 Marks Question
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13 Q→05M.C.Q (1 Marks)
176 Q→06Assertion (A) & Reason (B) MCQ
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32 Q→Sample Questions
Wave Optics questions
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Answer the following question:
As you have learnt in the text, the principle of linear superposition of wave displacement is basic to understanding intensity distributions in diffraction and interference patterns. What is the justification of this principle?
As you have learnt in the text, the principle of linear superposition of wave displacement is basic to understanding intensity distributions in diffraction and interference patterns. What is the justification of this principle?
What is the Brewster angle for air to glass transition? (Refractive index of glass = 1.5.)
The 6563 Å $\text{H}\alpha$ line emitted by hydrogen in a star is found to be redshifted by 15 Å. Estimate the speed with which the star is receding from the Earth.
View full solution →Estimate the distance for which ray optics is good approximation for an aperture of 4 mm and wavelength 400 nm.
Light of wavelength 5000 Å falls on a plane reflecting surface. What are the wavelength and frequency of the reflected light? For what angle of incidence is the reflected ray normal to the incident ray?
A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes in a Young’s double-slit experiment.
- Find the distance of the third bright fringe on the screen from the central maximum for wavelength 650 nm.
- What is the least distance from the central maximum where the bright fringes due to both the wavelengths coincide?
Answer the following question:
Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily.
Two students are separated by a 7 m partition wall in a room 10 m high. If both light and sound waves can bend around obstacles, how is it that the students are unable to see each other even though they can converse easily.
For sound waves, the Doppler formula for frequency shift differs slightly between the two situations: (i) source at rest; observer moving, and (ii) source moving; observer at rest. The exact Doppler formulas for the case of light waves in vacuum are, however, strictly identical for these situations. Explain why this should be so. Would you expect the formulas to be strictly identical for the two situations in case of light travelling in a medium?
In a Young’s double-slit experiment, the slits are separated by 0.28 mm and the screen is placed 1.4 m away. The distance between the central bright fringe and the fourth bright fringe is measured to be 1.2 cm. Determine the wavelength of light used in the experiment.
Answer the following question:
In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?
In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?
Answer the following question:
When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why?
When a tiny circular obstacle is placed in the path of light from a distant source, a bright spot is seen at the centre of the shadow of the obstacle. Explain why?
Answer the following question:
When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. Suggest a possible explanation.
When a low flying aircraft passes overhead, we sometimes notice a slight shaking of the picture on our TV screen. Suggest a possible explanation.
To which part of the electromagnetic spectrum does a wave of frequency 5 x 1011 Hz belong?
To which part of the electromagnetic spectrum does a wave of frequency 3 x 1013 Hz belong?
For a single slit of width "a", the first minimum of the interference pattem of a monochromatic light of wavelength$\lambda$. Occurs at an angle of$\frac{\lambda}{\text{a}}$. At the same angle of$\frac{\lambda}{\text{a}},$ we get a maximum for two narrow slits separated by a distance "a". Explain.
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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.
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?
Huygen's principle is the basis of wave theory of light. Each point on a wavefront acts as a fresh source of new disturbance, called secondary waves or wavelets. The secondary wavelets spread out in all directions with the speed light in the given medium.
An initially parallel cylindrical beam travels in a medium of refractive index $\mu(\text{I})=\mu_0+\mu_2\text{I}$, where $\mu_0$ and $\mu_2$ are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius.
View full solution →An initially parallel cylindrical beam travels in a medium of refractive index $\mu(\text{I})=\mu_0+\mu_2\text{I}$, where $\mu_0$ and $\mu_2$ are positive constants and I is the intensity of the light beam. The intensity of the beam is decreasing with increasing radius.
- The initial shape of the wavefront of the beam is:
- Planar.
- Convex.
- Concave.
- Convex near the axis and concave near the periphery.
- According to Huygens Principle, the surface of constant phase is:
- Called an optical ray.
- Called a wave.
- Called a wavefront.
- Always linear in shape.
- As the beam enters the medium, it will:
- Travel as a cylindrical beam.
- Diverge.
- Converge.
- Diverge near the axis and converge near the periphery.
- Two plane wavefronts oflight, one incident on a thin convex lens and another on the refracting face of a thin prism. After refraction at them, the emerging wavefronts respectively become.
- Plane wavefront and plane wavefront.
- Plane wavefront and spherical wavefront.
- Spherical wavefront and plane wavefront.
- Spherical wavefront and spherical wavefront.
- Which of the following phenomena support the wave theory of light?
- Scattering.
- Interference.
- Diffraction.
- Velocity of light in a denser medium is less than the velocity of light in the rarer medium.
- 1, 2, 3
- 1, 2, 4
- 2, 3, 4
- 1, 3, 4
The resolving power of a telescope can be increased by increasing:
- AWavelength of light.
- BDiameter of objective.
- CLength of the tube.
- DFocal length of eyepiece.
The colour of bright fringes nearest to the central achromatic fringe in the interference pattern with white light will be:
- AViolet
- BRed
- CGreen
- DYellow
Why do polarized sun glasses block out some reflected light (glare), but do not block out light that has not been reflected?
- ASome reflected light is at least partially polarized.
- BSome reflected light changes frequency.
- CSome reflected light is at least partially diffracted.
- DSome reflected light splits into multiple photons.
If one of the two slits of Young's double-slit experiment is painted so that it transmits half the light intensity as the second slit, then:
- AFringe system will altogether disappear.
- BBright fringes will become brighter and the dark fringes will become darker.
- CBoth dark and bright fringes will become darker.
- DDark fringes will become less dark and bright fringes will become less bright.
A very thin film in reflected white light appears:
- AViolet
- BWhite
- CBlack
- DRed
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason (R): Wave diffracted from the edges of circular obstacle interfere constructively at the centre of the shadow resulting in the formation of bright spot.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is NOT the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason (R): Wave diffracted from the edges of circular obstacle interfere constructively at the centre of the shadow resulting in the formation of bright spot.
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason (R): In the figure of assertion the distance |S1P - S2P| is equal to distance |S2Q- S1Q|.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is NOT the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason (R): In the figure of assertion the distance |S1P - S2P| is equal to distance |S2Q- S1Q|.
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason (R): Destructive interference occurs at the centre of the shadow.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is NOT the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason (R): Destructive interference occurs at the centre of the shadow.
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason (R): In interference fringe width is independent of position of the fringe.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is NOT the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason (R): In interference fringe width is independent of position of the fringe.
For question two statements are given-one labelled Assertion (A) and the other labelled Reason (R). Select the correct answer to these questions from the codes (a), (b), (c) and (d) as given below.
Reason (R): For a dark fringe intensity is zero.
- Both A and R are true and R is the correct explanation of A.
- Both A and R are true but R is NOT the correct explanation of A.
- A is true but R is false.
- A is false and R is also false.
Reason (R): For a dark fringe intensity is zero.
In Young’s double-slit experiment using monochromatic light of wavelength λ, the intensity of light at a point on the screen where path difference is λ, is K units. What is the intensity of light at a point where path difference is λ/3?
Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of (a) reflected, and (b) refracted light? Refractive index of water is 1.33.
Let us list some of the factors, which could possibly influence the speed of wave propagation:
- Nature of the source.
- Direction of propagation.
- Motion of the source and/or observer.
- Wavelength.
- Intensity of the wave.
- The speed of light in vacuum,
- The speed of light in a medium (say, glass or water), depend?
Using Huygens’ Principle, draw a diagram to show propagation of a wavefront originating from a monochromatic point source. Explain briefly.
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