20 questions
The bluish colour of water in deep sea is due to:
The presence of algae and other plants found in water
Reflection of the sky in water
Scattering of light
Absorption of light by the sea
The layer of atmosphere whose temperature is less than that of hotter layer behaves as an optically
Denser medium
Rarer medium
Inactive medium
Either denser or rarer medium
A 10 mm long awl pin is placed vertically in front of a concave mirror. A 5 mm long image of the awl pin is formed at 30 cm in front of the mirror. The focal length of this mirror is
30 cm
20 cm
40cm
60 cm
Under which of the following conditions a concave mirror can form an image larger than the actual object?
When the object is kept at a distance equal to its radius of curvature
When object is kept at a distance less than its focal length
When object is placed between the focus and centre of curvature
When object is kept at a distance greater than its radius of curvature
A light ray enters from medium A to medium B as shown in figure. The refractive index of medium B relative to A will be
Greater than unity
Less than unity
Equal to unity
Zero
Which of the following statements is true?
A convex lens has -4 dioptre power having a focal length 0.25 m
A concave lens has 4 dioptre power having a focal length 0.25 m
A concave lens has -4 dioptre power having a focal length 0.25 m.
A convex lens has 4 dioptre power having a focal length 0.25 m
A child is standing in front of a magic mirror. She finds the image of her head bigger, the middle portion of her body of the same size and that of the legs smaller. The following is the order of combinations for the magic mirror from the top.
Plane, convex and concave
Convex, concave and plane
Concave, plane and convex
Convex, plane and concave
The deviation of light ray from its path when it travels from one transparent medium to another transparent medium is called
Reflection
Refraction
Dispersion
Scattering
A student used a device (X) to obtain/focus the image of a well illuminated distant building on a screen (S) as shown alongside in the diagram. Select the correct statement about the device (X).
This device is a concave lens of focal length 8 cm.
This device is a convex mirror of focal length 8 cm.
This device is a convex lens of focal length 4 cm.
This device is a convex lens of focal length 8 cm.
The mirror having reflecting surface curved inwards
Plane mirror
Convex mirror
Concave mirror
Cylindrical mirror
If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed at a distance of 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:
20 cm
10 cm
18 cm
5 cm
Which of the following can make a parallel beam of light from a point source incident on it?
Concave mirror as well as convex lens
Convex mirror as well as concave lens
Two plane mirrors placed at 90degree to each other
Concave mirror as well as concave lens
Twinkling of stars is due to atmospheric
Dispersion of light by water droplets
Refraction of light by different layers of varying refractive indices
Scattering of light by dust particles
Internal reflection of light by clouds
The danger signals installed at the top of tall buildings are red in colour. These can be easily seen from a distance because among all other colours, the red light
is scattered the most by smoke or fog.
is scattered the least by smoke or fog.
is absorbed the most by smoke or fog.
moves fastest in air.
A student traces the path of a ray through a glass prism for four different values of angle of incidence. On analyzing the diagrams he is likely to conclude that the emergent ray
is always parallel to the incident ray.
is always perpendicular to the incident ray.
is always parallel to the refracted ray.
always bends at an angle to the direction of incident ray.
The splitting of white light into its component colours is called
Refraction
Reflection
Dispersion
Tyndall effect
Which of the following colours is the least deviated on passing through a prism :
Red
Yellow
Violet
Indigo
The star appear shifted from their actual position due to the phenomenon of:
Diffraction of light
Scattering of light
Refraction of light
Reflection of light
Which of the following phenomena contributes significantly to the reddish appearance of the sun at sunrise or sunset?
Dispersion of light
Scattering of light
Total internal reflection of light
Reflection of light from the earth
Assertion(A): A convex mirror is used as a rear view/Driver's mirror.
Reason(R): Convex mirrors have a wider field of view as they are curved outwards. They also give an erect, although diminished image.
Both (A) and (R) are true, and (R) is the correct explanation of the assertion.
Both (A) and (R) are true , but (R) is not the correct explanation of the Assertion.
(A) is true, but (R) is false.
(A) is false, but (R) is true,