Ray Optics Test

Result

Ray Optics Test - 151

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Weekly Quiz Competition

Question 1
4 / -1

If tube length of astronomical telescope is 105 cm and magnifying power is 20 for normal setting, calculate the focal length of objective

A
100 cm

B
10 cm

C
20 cm

D
25 cm

Solution
Question 2
4 / -1

The length of a telescope is 36 cm. The focal lengths of its lenses can be

A
30 cm, 6 cm

B
– 30 cm, – 6 cm

C
30 cm, –6 cm

D
– 30 cm, 6 cm

Solution
Question 3
4 / -1

An astronomical telescope of ten-fold angular magnification has a length of 44 cm. The focal length of the objective is

A
4 cm

B
40 cm

C
44 cm

D
440 cm

Solution
Question 4
4 / -1

If both the object and image are at infinite distance from a refracting telescope its magnifying power will be equal to

A
The sum of the focal lengths of the objective and the eyepiece

B
The difference of the focal lengths of the two lenses

C
The ratio of the focal length of the objective and eyepiece

D
The ratio of the focal length of the eyepiece and objective

Solution
Question 5
4 / -1

The focal lengths of the objective and eyepiece of a telescope are respectively 100 cm and 2 cm. The moon subtends an angle of 0.5° at the eye. If it is looked through the telescope, the angle subtended by the moon\'s image will be

A
100°

B
50°

C
25°

D
10°

Solution
Question 6
4 / -1

The diameter of the objective of a telescope is a, its magnifying power is m and wavelength of light is λ. The resolving power of the telescope is

A
(1.22 λ )/a

B
(1.22a) / λ

C
λm / (1.22a)

D
a / (1.22λ)
Question 7
4 / -1

The magnifying power of a telescope is 9. When it is adjusted for parallel rays the distance between the objective and eyepiece is 20 cm. The focal length of lenses are

A
10 cm, 10 cm

B
15 cm, 5 cm

C
18 cm, 2 cm

D
11cm, 9 cm

Solution
Question 8
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 9
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 10
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