Ray Optics Test

Result

Ray Optics Test - 96

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Weekly Quiz Competition

Question 1
4 / -1

The distance between a point source of light and a screen which is 60 cm is increased to 180 cm. The intensity on the screen as compared with the original intensity will be

A
(1/9) times

B
(1/3) times

C
3 times

D
9 times

Solution
Question 2
4 / -1

A source of light emits a continuous stream of light energy which falls on a given area. Luminous intensity is defined as

A
Luminous energy emitted by the source per second

B
Luminous flux emitted by source per unit solid angle

C
Luminous flux falling per unit area of a given surface

D
Luminous flux coming per unit area of an illuminated surface
Question 3
4 / -1

Venus looks brighter than other stars because

A
It has higher density than other stars

B
It is closer to the earth than other stars

C
It has no atmosphere

D
Atomic fission takes place on its surface

Solution
Question 4
4 / -1

To prepare a print the time taken is 5 sec due to lamp of 60 watt at 0.25 m distance. If the distance is increased to 40 cm then what is the time taken to prepare the similar print

A
3.1 s

B
1 s

C
12.8 s

D
16 s

Solution
Question 5
4 / -1

A lamp is hanging lm above the centre of a circular table of diameter lm. The ratio of illuminaces at the centre and the edge is

A

B

C

D

Solution
Question 6
4 / -1

A lamp is hanging at a height of 4m above a table. The lamp is lowered by lm. The percentage increase in illuminace will be

A
40%

B
64%

C
78%

D
92%

Solution
Question 7
4 / -1

The intensity of direct sunlight on a surface normal to the rays is I₀. What is the intensity of direct sunlight on a surface, whose normal makes an angle of 60° with the rays of the sun

A

B

C

D

Solution
Question 8
4 / -1

Inverse square law for illuminance is valid for

A
Isotropic point source

B
Cylindrical source

C
Search light

D
All types of sources
Question 9
4 / -1

1% of light of a source with luminous intensity 50 candela is incident on a circular surface of radius 10 cm. The average illuminance of surface is

A
100 lux

B
200 lux

C
300 lux

D
400 lux

Solution
Question 10
4 / -1

Two light sources with equal luminous intensity are lying at a distance of 1.2 m from each other. Where should a screen be placed between them such that illuminance on one of its faces is four times that on another face

A
0.2 m

B
0.4 m

C
0.8 m

D
1.6 m

Solution