Question Pool Wave Optics

# Wave Optics - SAMAGRA Question Pool & Answers | Class 12

Kerala Syllabus SAMAGRA SCERT SAMAGRA Question Pool for Class 12 Physics Wave Optics

Qn 1.

A beam of light,with intensity I0, is passing through a polarizer and an analyzer as shown in figure.

(a)State Malus law related to the intensity of transmitted through the analyzer.

(b)If θ=450,What is the relation of the intensities of original light and transmitted light after passing through the analyzer?

(c) Which of the following waves can be polarized (i)X-rays (ii)sound waves Why?

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Qn 2.

Green light is incident at the Polarizing angle on a certain glass plate as shown in figure.

(a) What do you mean by polarizing angle?

(b)Indicate the polarization components on the reflected and refracted rays, by arrows and dots.

(c)Find the refractive index of glass.

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Qn 3.

A slit S is illuminated by a monochromatic source of light to give two coherent source Pand P2.These give a dark band at the point R on the screen as shown in figure.

(a) Write the formula to find out band width.

(b)What relationship must exist between the lengths P1R and P2R?

(c)Can interference fringes be produced by using two identical bulbs?

(d) If the distance between P1and P2 is 1mm and the screen is placed 1m away, what is the fringe separation for a light of wavelength 5x10-7 m ?

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Qn 4.

Light of wavelength 589 nm is used to view an object under a microscope. The aperture of the objective has a diameter of 0.900 cm.

(a)What do you mean by limit of resolution of an optical instrument?

(b) what is the limiting of resolution of the above microscope?

(c)What happens to the limit of resolution if the objective is immersed in oil? Explain.

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Qn 5.

A long narrow slit is illuminated by blue light and the diffraction pattern is obtained on a white screen.

(a) How the width of bands change as the distance from the centre increases? (b)What happens to the width of pattern, if yellow light is used instead of blue light?

(c)In a double slit experiment, the slits are separated by 0.03 cm and the screen is placed 1.5 m away. The distance between the central fringe and the fourth bright fringe is 1 cm. Determine the wavelength of light used in the experiment

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Qn 6.

The double slit in Young’s experiment is replaced by a single narrow slit (illuminated by a monochromatic source).Then,

(a)How the pattern of bands on the screen differ from the pattern due to double slit?

(b)Derive an expression for the band width of the central fringe.

(c)Draw a graph which shows the variation of intensity of light with distance .

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Qn 7.

According to a principle, at a particular point in a medium, the resultant displacement produced by a number of waves is the vector sum of the displacements produced by each of the waves.

(a) Name of the principle

(b)Derive an expression for the band width in young’s double slit experiment

(c) What are the conditions at which two light sources become coherent?

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Qn 8.

Consider a point source emitting waves uniformly in all directions.

(a) Draw two wave fronts very near to the point source

(b)Using Huygen’s principle ,prove that angle of incidence is equal to angle of reflection.

(c)What is the shape of a plane wave front after passing through a thin convex lens?

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Qn 9.

If Young’s double slit experiments appartus is immersed in a liquid of n = 1.33. What will happen to the fringe width of the interference pattern? Explain.

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Qn 10.

A student performs an interference experiment in the laboratory using two pointcoherent sources, Sand S2 separated by a distance ‘d’ and obtained the interference pattern on a screen at a distance ‘D’ from the sources as in fig.

a) What will be the shape of wavefronts from sources S 1 and S 2

b) Write the condition that ‘P’ on the screen appears bright and find its fringe width.

c) If the screen is at a distance 1m from S 1 and S 2 , width of fringes obtained is 1.5mm. Find the separation between sources if they produce a wavelength 7000A0

a) Spherical

b) S1P-S2P= nλ, Derivation of equation of fringe

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Qn 11.

In order to observe good interference and diifraction pattern, the necessary and sufficient conditions are

I. the distance between the slits should be very small (~ mm)

II the slit width should be very small (~ mm)

III. the distance between the slits and the screen should be large (~ cm)

IV the distance between slits and the screen shou small (~ mm)

(a) I and II                              (b) I and III

(c) I, II and III                         (d) II and III

(c) I, II and III

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Qn 12.

The resolving power of a telescope is limited by

I. the focal length of objective lens

II. the diameter of objective lens

III. the wavelength of the light used

IV the thickness of the objective lens

(a) I and II                    (b) I, II and III

(c) II and III                   (d) I, III and IV

(c) II and

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Qn 13.

Which of the following statements are true abot diffraction pattern?

I. It has a central bright maxima of twice the wic other maxima.

II. The first null occurs at an angle λ/2a.

III. The intensity of maxima falls as we move away the central maxima.

IV The bands are of decreasing width.

(a) II and III                                      (b) I and II

(c) I, III and IV                                   (d) I and III

(d) I and

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Qn 14.

The conditions for producing sustained interference are

I. phase difference between interfering waves remains constant with time.

II. interfering waves have nearly same amplitude levels.

III. interfering waves are of same frequency.

IV interfering waves are moving in opposite directions,

(a) I, II and III                                            (b) II and III

(c) III and IV                                             (d) I and IV

(a) I, II and III

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Qn 15.

Which of the following cannot be explained on the basis of wave nature of light?

I.Polarization                                   II.Total internal reflection

III. Photoelectric effect                    IV. Crompton effect

(a) II  and  III                   (b) III and IV

(c) IV and I                       (d) III only

(b) III and

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Qn 16.

Which of the following statements is/are correct ?

(I)A point source emitting waves uniformly in all directions.

(II) In spherical wave, the locus of point which have the some amplitude and vibrate in same phase are spheres.

(III)At a small distance from the source, a small portion of sphere can be considered as plane wave.

(a) Only                  (b) I and II

(c) Only III              (d) I, II and III

(b) I and

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Qn 17.

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.

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Qn 18.

What is the shape of the wavefront from a distant star intercepted by the Earth.

The portion of the wavefront of light from a distant star intercepted by the Earth is a

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Qn 19.

2)What is the shape of the wavefront in each of the following cases:

(a) Light diverging from a point source.

(b) Light emerging out of a convex lens when a point source is placed at its focus.

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Qn 20.

a)The refractive index of glass is 1.5. What is the speed of light in glass? Speed of light in vacuum is 3.0 × 108 m s−1)

(b) Is the speed of light in glass independent of the colour of light? If not, which of the two colours red and violet travels slower in a glass prism?

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Qn 21.

In Young"s  double-slit experiment the angular width of a fringe is found to be 0.2° on a screen placed 1 m away. The wavelength of light used is 600 nm. What will be the angular width of the fringe if the entire experimental apparatus is immersed in water? Take refractive index of water to be 4/3.

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Qn 22.

In double-slit experiment using light of wavelength 600 nm, the angular width of a fringe formed on a distant screen is 0.1º. What is the spacing between the two slits?

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Qn 23.

The 6563 Å    line emitted by hydrogen in a star is found to be red shifted by 15 Å. Estimate the speed with which the star is receding from the Earth.

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Qn 24.

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.

Bending of waves by obstacles by a large angle is possible when the size of the obstacle is comparable to the wavelength of the

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Qn 25.

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

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Qn 26.

In what way is diffraction from each slit related to the interference pattern in a double-slit experiment?

he interference pattern in a double-slit experiment is modulated by diffraction from each slit. The pattern is the result of the

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Qn 27.

In a single slit diffraction experiment, the width of the slit is made double the original width. How does this affect the size and intensity of the central diffraction band ?

In a single slit diffraction experiment, if the width of the slit is made double the original width, then the size of the central

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Qn 28.

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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Qn 29.

.Draw th intensity distribution graph in young's double slit experiment.

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Qn 30.

Draw the intensity distribution graph of diffraction pattern?

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Qn 31.

Wave front is a concept introduced by Huygens to explain various optical phenomena.

a) What type of wave front will emerge from

i) A point source                  ii) Distant source of light

b) A plane wave front is incident normally on a convex lens. Sketch the refracted wave front.

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Qn 32.

Figure given below shows the arrangement to test the polarization of light waves.(θ is the angle between P1 and P2 )

a)Name and state the law relating intensity of light emerging from the Polaroid P2 and θ

b)Draw a graph showing angular dependence of intensity of plane polarized light emerging from the second polarizer P2 .

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Qn 33.

On what factors the magnifying power and resolving power of refracting type telescope depend ?

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Qn 34.

i) Name the phenomenon which proves the transverse nature of light?

ii)Name a device which uses this phenomenon?

iii)Give two uses of the devices whose functioning is based on this phenomenon?

i) Polarisation.

ii) Polaroid

iii) In 3D

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Qn 35.

How does the resolving power of a compound microscope change when

i) refractive index of the medium between the object and the object lens increases ii)when the wavelength of the radiation used is increased

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Qn 36.

Distinguish between magnifying power and resolving power of a telescope?

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Qn 37.

Does the value of polarizing angle of incidence depend on the colour of light?

Yes.

The refractive index of material depends upon the colour or wavelength of light .As

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Qn 38.

State true or false and give reason

“Ultrasonic wave does not show the property of polarization’ .

The statement is true. Ultrasonic wave is a sound wave and it is longitudinal in

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Qn 39.

Name the special characteristic of light wave which is demonstrated only by the phenomenon of polarization?

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Qn 40.

Oil immersion microscope has higher resolving power than ordinary microscope why?

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Qn 41.

How does the resolving power of a telescope change when the aperture of objective is increased?

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Qn 42.

Why does a soap bubble or thin film of oil show beautiful colours when illuminated by white light? Explain.

It is due to interference of light.

Light waves reflected from the upper and lower part of

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Qn 43.

In Young’s Double slit experiment ,monochromatic source is replaced by white light .What happens to the interference bands?

A white band is formed at the centre and coloured bands are formed on either

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Qn 44.

State the essential condition for diffraction of light to occur?

he size of the obstacle or aperture should be of the order of wavelength of

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Qn 45.

Interference of light obeys the law of conservation of energy’.Whether the statement is true or false? Justify your answer.

True.

In interference, there is a re-distribution of energy take place from the region of

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Qn 46.

Explain the statement ‘Light added to light can produce darkness’?

When light waves of same amplitude meet at point in opposite phases, the resultant amplitude and hence the intensity becomes zero at that

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Qn 47.

No inteterference pattern is observed when two coherent sources are far apart .Explain why?

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Qn 48.

No inteterference pattern is observed when two coherent sources are infinitely close to one another. Explain Why?

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Qn 49.

A and B are two points on a water surface where waves are generated. What is the phase difference if

a)A and B are on the same wavefront but separated in distance by the wave length λ.

b)A and B are on successive troughs.

a)Zero

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Qn 50.

What will be the phase change when a ray under goes refraction?

No change in

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Qn 51.

What will be the phase change when a ray under goes reflection?

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Qn 52.

Can two wavefronts cross onanother? Give reason.

No.

If they intersect there will be two rays (directions of propagation of energy)at the

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Qn 53.

Two coherent monochrometic light beams of intensities I and

4I are superimposed. What is the maximum and minimum

possible intensities in the resulting beam ?

Amplitude ,a1 =2 √I and a2= √I

;

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Qn 54.

When a tiny circular obstacle is placed in the path of light form

a distant source, a bright spot is seen at the centre of the shadow of

the obstacle Explain why?

Waves diffracted from the edge of the circular obstacle interfere constructively at the centre of the shadow producing bright

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Qn 55.

When a low flying air craft passes over the head we some times

notice slight shaking of the picture on our TV screen. Explain. ?

Interference of the direct signal received by the antenna with the signal reflected by the

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Qn 56.

What is effect of temperature variation on the refractive index of a medium?

As the temperature increases refractive index μ