CBSE Class 10 Physics Case Study Questions Light Reflection and Refraction MCQs

Case/Passage – 1
A 5.0 cm tall object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm.

Question: What is the power of the used lens?
(a) + 5 D
(b) – 5 D
(c) + 0.5 D
(d) – 0.5 D   

Answer: A

Question: What is the distance of image from the pole of lens?
(a) v = 60 cm
(b) v = – 60 cm
(c) v = 30 cm
(d) v = –30 cm 

Answer: A

Case/Passage – 2
Light travels through a vacuum at a speed c = 3 × 108 m/s. It can also travel through many materials, such as air, water and glass. Atoms in the material absorb, reemit and scatter the light, however. Therefore, light travels through the material at a speed that is less than c, the actual speed depending on the nature of the material. To describe the extent to which the speed of light in a material medium differs from that in a vacuum, we use a parameter called the index of refraction (or refractive index).

Question: Figure shows a ray of light as it travels from medium A to 

medium B. Retractive index of the medium B relative to medium A is
(a) √3/2
(b)√2/3
(c)√1/2
(d) √2

Answer: A

Question:The path of a ray of light coming from air passing through a rectangular glass slab traced by four students shown as A, B, C and D in the figure. Which one of them is correct?

(a) A
(b) B
(c) C
(d) D   

Answer: B

Question: A light ray enters from medium A to medium B as shown  

in the figure. The refractive index of medium B relative to A will be
(a) greater than unity
(b) less than unity
(c) equal to unity
(d) zero

Answer: A

Question: You are given water, mustard oil, glycerine and kerosene. 
In which of these media, a ray of light incident obliquely at same angle would bend the most?
(a) Kerosene
(b) Water
(c) Mustard oil
(d) Glycerine   

Answer: D

Question: A ray of light is incident in medium 1 on a surface that separates medium 1 from medium 2. Let v1 and v2 represent the velocity of light in medium 1 and medium 2 respectively. Also let n12 and n21 represent the refractive index of medium 1 with respect to medium 2 and refractive index of medium 2 with respect to medium 1, respectively. If i and r denote the angle of incidence and angle of refraction, then-
(a) sin i/sin r = n21V1/V2
(b) sin i/sin r = n21V2/V1
(c) sin i/sin r = n12V1/V2
(d) sin i/sin r = n12 V2/V1   

Answer: A

Case/Passage – 3
Inside a substance such as glass or water, light travels more slowly than it does in a vacuum. If c denotes the speed of light in a vacuum and v denotes its speed through some other substance, then v = c/n where n is a constant called the index of refraction. To good approximation, a substance’s index of refraction does not depend on the wavelength of light. For instance, when red and blue light waves enter water, they both slow down by about the same amount. More precise measurements, however, reveal that n varies with wavelength. Table presents some indices of refraction of Custon glass, for different wavelengths of visible light. A nanometer (nm) is 10–9 meters. In a vacuum, light travels as c = 3.0 × 108 m/s 

Question: Inside Custon glass
(a) Orange light travels faster than yellow light
(b) Yellow light travels faster than orange light
(c) Orange and Yellow light travels equally fast
(d) We cannot determine which color of light travels faster 

Answer: A

Question: Which of the following phenomena happens because n varies with wavelength
(a) A lens focuses light
(b) A prism breaks sunlight into different colors
(c) Total internal reflections ensures that light travels down a fiber optic cable
(d) Light rays entering a pond change direction at the pond’s surface 

Answer: B

Question: For blue-green of wavelength 520 nm, the index of refraction of Custon glass is probably closest to
(a) 1.49
(b) 1.50
(c) 1.51
(d) 1.52 

Answer: C

Case Study Based Questions

I. An image formed in a convex mirror is always virtual,erect and smaller in size whatever be the position of the object. However in a concave mirror the image may be real or virtual: erect or inverted :smaller or bigger in size than the object. This would depend upon the distance of the object from the mirror.

Question: A Concave mirror is used as reflector in
A. Torches
B. Search lights
C. Head lights of motor vehicles
D. All the above

Answer: D

Question: In street lamps,the reflector used is a
A. Convex mirror
B. Concave mirror
C. Plane mirror
D. None of these

Answer: A

Question: Which of the mirrors has larger field of view ?
A. Convex
B. Concave
C. plane
D. all have same field of view

Answer: A

Question: Real or virtual image of an object formed by a concave mirror depends on
A. Size of mirror
B. Polish of mirror
C. Distance of object from the mirror
D. All of these

Answer: C

II. The image of an object formed by a convex lens may be real/virtual: erect/inverted; smaller/larger than the object. It would depend upon distance of the object from the lens. however, the image of an object formed by a concave lens is always virtual, erect and smaller in size than the object.

Question: Question: to obtain image of an object on a screen jwe require a
A. Convex lens
B. Concave lens
C. Concave lens of large focal length
D. Concave lens of small focal length

Answer: A

Question: Where an object should be placed in front of a concave lens to obtain a virtual image of the object?
A. Infinity
B. Principal focus
C. Very close to the lens
D. Any distance from the lens

Answer: D

Question: Where should an object be placed in front or a convex lens to obtain image of the size of the object ?
A. At focus F
B. At 2 F
C. Beyond 2 F
D. None of these

Answer: B

Question: To obtain an image smaller than the size of the object, we may used a
A. Convex lens only
B. Concave lens only
C. Either a convex lens or a concave lens
D. Cannot say

Answer: C

III. The scattering involves bouncing off of light by atoms/molecules of the medium through which they are travelling. Most of the beautiful phenomena like blue colour of sky, white colour of clouds, red hues of sunrise and sunset have been explained in terms of scattering of light. Lord Rayleigh studied elastic scattering and established that intensity of scattered light (Is) varies inversely as the fourth power of wavelength (ℷ) of incident light. The only condition for Rayleigh scattering to be valid is that size of scatterer (x) must be much less than the wavelength (ℷ) of light.

Question: Rayleigh scattering accounts for
A. Blue colourof sky
B. White colour of clouds
C. Red hues of sunrise and sunset
D. All the above

Answer: C

Question: The essential condition for rayleigh’s scattering is the size (x) of scatterer must be
A. Much smaller wave length (ℷ) of light
B. Much grater then the wave length of light
C. Equal to wave length of light
D. Cannot say

Answer: D

Question: In Rayleigh scattering intensity of scattered light (Is) varies inversely as power (n) of wave length (ℷ) of light, where n =
A. 6
B. 8
C. 4
D. 2

Answer: C

Question: Rayleigh scattering accounts for
A. Blue colour of sky
B. White colour of clouds
C. Red hues of sun rise and sun set
D. All the above

Answer: B