Ray Optics Test

Result

Ray Optics Test - 95

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Weekly Quiz Competition

Question 1
4 / -1

Correct exposure for a photographic print is 10 seconds at a distance of one metre from a point source of 20 candela. For an equal fogging of the print placed at a distance of 2 m from a 16 candela source, the necessary time for exposure is

A
100 s

B
25 s

C
50 s

D
75 s

Solution
Question 2
4 / -1

A bulb of 100 watt is hanging at a height of one meter above the centre of a circular table of diameter 4 m. If the intensity at a point on its rim is I₀, then the intensity at the centre of the table will be

A

B

C

D

Solution
Question 3
4 / -1

A movie projector forms an image 3.5m long of an object 35 mm. supposing there is negligible absorption of light by aperture then illuminance on slide and screen will be in the ratio of

A
100 : 1

B
10⁴ : 1

C
1 : 100

D
1 : 10⁴

Solution
Question 4
4 / -1

A 60 watt bulb is hung over the center of a table 4 m × 4 m at a height of 3 m. The ratio of the intensities of illumination at a point on the centre of the edge and on the corner of the table is

A
(17/13)^3/2

B
2/1

C
17/13

D
5/4

Solution
Question 5
4 / -1

If the luminous intensity of a 100 W unidirectional bulb is 100 candela, then total luminous flux emitted from the bulb is

A
861 lumen

B
986 lumen

C
1256 lumen

D
1561 lumen

Solution
Question 6
4 / -1

The maximum illumination on a screen at a distance of 2 m from a lamp is 25 lux. The value of total luminous flux emitted by the lamp is

A
1256 lumen

B
1600 lumen

C
100 candela

D
400 lumen

Solution
Question 7
4 / -1

A small lamp is hung at a height of 8 feet above the centre of a round table of diameter 16 feet. The ratio of intensities of illumination at the centre and at points on the circumference of the table will be

A
1 : 1

B
2 : 1

C

D
3 : 2

Solution
Question 8
4 / -1

Lux is equal to

A
1 lumen/m²

B
1 lumen/cm²

C
1 candela/m²

D
1 candela/cm²

Solution
Question 9
4 / -1

Five lumen/watt is the luminous efficiency of a lamp and its luminous intensity is 35 candela. The power of the lamp is

A
80 W

B
176 W

C
88 W

D
36 W

Solution
Question 10
4 / -1

A lamp rated at 100 cd hangs over the middle of a round table with diameter 3 m at a height of 2 m. It is replaced by a lamp of 25 cd and the distance to the table is changed so that the illumination at the centre of the table remains as before. The illumination at edge of the table becomes X times the original. Then X is

A
1/3

B
16/27

C
1/4

D
1/9

Solution