# MCQ Questions for Class 12 Physics Chapter 9 Ray Optics and Optical Instruments with Answers

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## Ray Optics and Optical Instruments Class 12 MCQs Questions with Answers

Solve this Ray Optics and Optical Instruments Multiple Choice Questions of Class 12 Physics Chapter 9 MCQ, so as not to miss out on any concept from being clear about what they mean!

Question 1.
Ashort pulse of white light is incident from air to a glass slab atnormal incidence. After travelling through the slab, the first colour to emerge is
(a) blue.
(b) green.
(c) violet.
(d) red.

Question 2.
You are given four sources of light each one providing a light of a single colour – red, blue, green and yellow. Suppose the angle of refraction for a beam of yellow light corresponding to a particular angle of incidence at the interface of two media is 90°. Which of the following statements is correct if the source of yellow light is replaced with that of other lights without changing the angle of incidence?
(a) The beam of red light would undergo total internal reflection.
(b) The beam of red light would bend towards normal while it gets refracted through the second medium.
(c) The beam of blue light would undergo total internal reflection.
(d) The beam of green light would bend away from the normal as it gets refracted through the second medium.

Answer: (c) The beam of blue light would undergo total internal reflection.

Question 3.
The optical density of turpentine is higher than that of water while its mass density is lower. Figure shows a layer of turpentine floating over water in a container. For which one of the four rays incident on turpentine in figure, the path shown is correct? (a) 1.
(b) 2
(c) 3
(d) 4

Question 4.
There are certain material developed in laboratories which have a negative refractive index (figure). A ray incident from air (medium 1) into such a medium (medium 2) shall follow a path given by Question 5.
Consider an extended object immersed in water contained in a plane trough. When seen from close to the edge of the trough the object will not look distorted because
(a) the apparent depth of the points close to the edge are nearer the surface of the water compared to the points away from the edge.
(b) the angle subtended by the image of the object at the eye is smaller than the actual angle subtended by the object in air.
(c) some of the points of the object far away from the edge may not be visible because of total internal reflection.
(d) water in a trough acts as a lens and magnifies the object.

Answer: (d) water in a trough acts as a lens and magnifies the object.

Question 6.
A rectangular block of glass ABCD has a refractive index 1.6. A pin is placed midway on the face AB (figure). When observed from the face AD, the pin shall (a) appear to be near A.
(b) appear to be near D.
(c) appear to be at the centre of AD.
(d) not be seen at all.

Answer: (d) not be seen at all.

Question 7.
An astronomical refractive telescope has an objective of focal length 20 m and an eyepiece of focal length 2 cm. Which one of the following is not possible?
(a) The length of the telescope tube is 20.02 m.
(b) The magnification is 1000.
(c) The image formed is inverted.
(d) An objective of a larger aperture will increase the brightness and reduce chromatic aberration of the image.

Answer: (d) An objective of a larger aperture will increase the brightness and reduce chromatic aberration of the image.

Question 8.
An object is placed at a distance of 40 cm from a concave mirror of focal length 15 cm. If the object is displaced through a distance of 20 cm towards the mirror, the displacement of the image will be:
(a) 30 cm away from the mirror
(b) 36 cm away from the mirror
(c) 30 cm towards the mirror
(d) 36 cm towards the mirror

Answer: (b) 36 cm away from the mirror

Question 9.
The refractive index of the material of a prism is √2 and the angle of the prism is 30°. One of the two refracting surfaces of the prism is made a mirror inwards, by silver coating. A beam of monochromatic light entering the prism from the other face will retrace its path (after reflection from the silvered surface) if its angle of incidence on the prism is:
(a) 60°
(b) 45°
(c) 30°
(d) zero

Question 10.
A diverging lens with magnitude of focal length 25 cm is placed at a distance of 15 cm from a converging lens of magnitude of focal length 20 cm. A beam of parallel light falls on the diverging lens. The final image formed is:
(a) real and at a distance of 40 cm from the divergent lens
(b) real and at a distance of 6 cm from the convergent lens
(c) real and at a distance of 40 cm from convergent lens
(d) virtual and at a distance of 40 cm from convergent lens.

Answer: (c) real and at a distance of 40 cm from convergent lens

II. Fill in the blanks

Question 1.
The bouncing back of light when it strikes a smooth or polished surface is called …………….. of light.

Question 2.
When light is reflected from a polit, surface the angle of incidence is …………… to the angle of reflection.

Question 3.
The image formed by a plane mirror shows …………….. inversion.

Question 4.
A plane drawn perpendicular to the principal axis and passing through the principal focus is called ………………. plane.

Question 5.
The size of the mirror is called its …………………..

Question 6.
The focal length of a spherical mirror is ……………….. its radius of curvature.

Question 7.
…………….. mirror is used as a rear-view mirror in automobiles.

Question 8.
A real image ………………… be focused on a screen.

Question 9.
A virtual image ……………… be focused or e screen.

Question 10.
The mirror formula is ……………….

Answer: $$\frac { 1 }{f}$$ = $$\frac { 1 }{u}$$ + $$\frac { 1 }{v}$$

Question 11.
The magnification produced by a spherical mirror is given by …………….

Answer: m = –$$\frac { v }{u}$$

Question 12.
If m is ………………. the image is erect w.r,t the object.

Question 13.
If m is ……………….. the image is inverted w.r.t. the object.

Question 14.
The basic cause of refraction is change in ………………… of light in going from one medium to another.

Question 15.
……………… of light does not change when a ray of light moves from an optically rarer to an optically denser medium.

Question 16.
An air bubble in a jar of water shines brightly is an example of …………………

Question 17.
For the same angle of incidence, the angles of refraction in three different mediums A, B and C are 15°, 25° and 35° respectively, ……………. medium will the velocity of light be minimum.

Question 18.
Total internal reflection must occur when angle of incidence is more than the …………………

Question 19.
Total internal reflection will occur when ray of light travels from …………… medium to …………….. medium.

Question 20.
Due to refraction, the depth of an optically denser medium appears to be ……………. than its real depth.

Question 21.
Due to refraction of light the sun is seen …………….. minutes before actual sunrise.

Question 22.
A diamond sparkles due to ……………… of light.

Question 23.
A ray of light undergoes …………….. twice on passing through a prism.

Question 24.
One dioptre is …………….. of a lens of focal length ……………… metre.

Question 25.
The deviation through a prism is minimum when angle of incidence is equal to angle of ……………..

Question 26.
In the minimum deviation position, the refracted ray in the prism is ………………. to the base of prism.

Question 27.
In the minimum deviation position of a prism the angle of refraction is equal to ………………. angle of prism.

Question 28.
White light consists of …………….. colours.

Question 29.
The magnification for a concave lens is always ………………..

Question 30.
A convergent lens made of crown glass (refractive index 1.5) has focal length 20cm in air. If it is immersed in a liquid of refractive index 1.60, its focal length will be ……………..

Question 31.
If two thin lenses of power P1 and P2 are held in contact then the power of the combination will be ……………..

Question 32.
If thin lenses of focal length f1, f2, f3 are in contact, the effective focal length of their combination is ………………

Answer: $$\frac { 1 }{f}$$ = $$\frac { 1 }{f_1}$$ + $$\frac { 1 }{f_2}$$ + $$\frac { 1 }{f_3}$$

Question 33.
The total magnification m of the combination of three lenses of magnification m1, m2 and m3 is ………………..

Answer: m1 × m2 × m3

Question 34.
The magnifying power of a simple microscope is ………………. if f is small.