#### Optics English Medium Free Online Test 1 Mark Questions 2020-2021

10th Standard

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Science

Time : 00:19:00 Hrs
Total Marks : 19

Part A

19 x 1 = 19
1. Where should an object be placed so that a real and inverted image of same size is obtained by a convex lens

(a)

f

(b)

2f

(c)

infinity

(d)

between f and 2f

2. Power of a lens is –4D, then its focal length is

(a)

4m

(b)

–40m

(c)

–0.25 m

(d)

–2.5 m

3. Which of the following lens would you prefer to use while reading small letters found in a dictionary?

(a)

A convex lens of focal length 5 cm

(b)

A concave lens of focal length 5 cm

(c)

A convex lens of focal length 10 cm

(d)

A concave lens of focal length 10 cm

4. The velocity of light is _______

(a)

3x 10-8 ms-1

(b)

3 x 108  ms-1

(c)

3 x 108 km s-1

(d)

3 x 10-8 km s-1

5. The splitting up of white light into colours is called

(a)

reflection

(b)

refraction

(c)

scattering

(d)

dispersion

6. The scattered light in Raman scattering contains _____ lines

(a)

Rayleigh's

(b)

stokes

(c)

Antistokes

(d)

all above

7. A convex lens forms a virtual image if the object is

(a)

at F

(b)

At infinity

(c)

below F and 2 F

(d)

below the lens and the principal focus

8. When a person uses a convex lens as a simple magnifying glass, the object must be placed at a distance

(a)

less than one focal length

(b)

more than one focal length

(c)

less than twice focal length

(d)

more than twice the focal length

9. Convex lens forms a highly diminished, real and inverted image, when an object is at

(a)

infinity

(b)

F

(c)

below F & c

(d)

beyond 2 F

10. An object is placed 25 cm from a convex lens whose focal length is 10 cm. The image distance is _______ cm.

(a)

50

(b)

16.66

(c)

6.66

(d)

10

11. The change in the focal length of human eye is caused by

(a)

Pupil

(b)

Ciliary muscles

(c)

Cornea

(d)

Iris

12. When a person is myopic, he / she can clearly see

(a)

Both nearby & far off

(b)

Only nearby objects

(c)

Only far off objects

(d)

Neither nearby nor far off objects

13. In Astigmatism, eye cannot see

(a)

distance object

(b)

nearby object

(c)

parallel lines

(d)

both a & b

14. Magnification power of microscopes can be included by using of lengths

(a)

Large focal eye piece

(b)

Objective lens

(c)

Shorter focal length of the eye piece

(d)

Larger focal length of objective

15. In compound microscope, as compare to eye piece, objective lens has _____ focal length.

(a)

-ve focal length

(b)

Zero

(c)

Small

(d)

Large

16. As compare to single lens, compound microscope gives ______

(a)

Smaller of eye lens of an adult human being is a 3D

(b)

4D

(c)

5D

(d)

6D

17. An inverted image of the object is formed in _____

(a)

Simple microscope

(b)

Compound microscope

(c)

Astronomical microscope

(d)

Both b & c

18. In compound microscope ______ lenses are used.

(a)

2

(b)

3

(c)

4

(d)

1

19. To increase the magnification of the telescope, the focal length of the ______

(a)

Objective lens is small and eye lens is large

(b)

Objective lens is large and eye lens is small

(c)

Objective lens and eye lens are small

(d)

Objective lens and eye lens are large