Dakshana Cumulative Test Class 10 "Physics-I"

1] A convex lens forms a virtual image when an object is placed at a distance of 18 cm from it. The focal length must be

i. greater than 36 cm
ii. greater than 18 cm
iii. less than 36 cm
iv. less than 18 cm

2] An object is placed before a convex lens. The image formed

i. is always real
ii. may be real or virtual
iii. is always virtual
iv. is always erect

3] An object is placed before a concave lens. The image formed

i. is always erect
ii. may be erect or inverted
iii. is always inverted
iv. is always real

4] A lens has a power of +0.5 D. It is

i. a concave lens of focal length 5 m
ii. a convex lens of focal length 5 cm
iii. a convex lens of focal length 2 m
iv. a concave lens of focal length 2 m

5] Select the correct statement.

i. The image formed by a convex mirror can be taken on the screen
ii. A convex mirror can produce a parallel beam of light from a point source
iii. The image of'an object placed at the focus of a convex mirror will be formed at infinity
iv. A concave mirror can never form a virtual, diminished image

6] In a museum a child walks towards a large concave mirror. He will observe that

i. his real, erect image goes on decreasing in size
ii. his virtual, erect image goes on increasing in size
iii. his real, inverted image goes on increasing in size and suddenly it becomes virtual, erect and magnified
iv. his real, erect Image goes on diminishing in size and suddenly it becomes virtual, erect and magnified

7] The magnification of an object placed 10 cm from a convex mirror of radius of curvature 20 cm will be

i. 0.2
ii. 0.5
iii. 1
iv. Infinity

8] A concave mirror of focal length 10 cm produces an image five times as large as the object. If the image is in front of the mirror, the distance of the object from the mirror will be

i. 10 cm
ii. 12 cm
iii. 16 cm
iv. 20 cm

9] To form an image twice the size of the object, using a convex lens of focal length 20 cm, the object distance must be

i. < 20 cm
ii. > 20 cm
iii. < 20 cm and between 20 cm and 40 cm
iv. Cannot say

10] Refractive index of glass with respect to air is 3/2. Then, what is the refractive index of air with respect to glass?

i. 2/3
ii. 1
iii. 0
iv. 9/4

11] A convex lens of focal length f will form a real, magnified image of an object if the object is placed

i. anywhere beyond 2F
ii. anywhere beyond F
iii. between F and 2F
iv. between lens and F

12] When a thin convex lens is put in contact with a thin concave lens of the same focal length, the resultant combination has a focal length equal to

i. f/2
ii. 2f
iii. 0
iv. Infinity

13] A convex lens has a focal length f. It is cut into two parts along the dotted line as shown in the figure. The focal length of each part will be

i. f/2
ii. f
iii. 3f/2
iv. 2f

14] A person is looking at the image of his face in a mirror by holding it close to his face. The image is virtual. When he moves the mirror away from his face, the image is inverted. What type of mirror is he using?

i. Plane mirror
ii. Convex mirror
iii. Concave mirror
iv. None of these

15] State the relation between refractive indices μ, μ₁ and μ₂ if the behaviour of light rays is as shown in the given figure.

i. μ > μ₂ > μ₁
ii. μ < μ₂ < μ₁
iii. μ < μ₂ : μ = μ₁
iv. μ₂ < μ₁ : μ = μ₂

16] A lens of power +2.0D is placed in contact with another lens of power –1.0D, the combination will behave like

i. A converging lens of focal length 100 cm
ii. A diverging lens of focal length 100 cm
iii. A converging lens of focal length 50 cm
iv. A diverging lens of focal length 50 cm

17] Which one of the following statements is correct for spherical mirrors ?

i. A concave mirror forms only virtual images for any position of the object
ii. A convex mirror forms only virtual images for any position of the object
iii. A concave mirror forms only a virtual, diminished image of an object placed between its pole and the focus
iv. A convex mirror forms a virtual, magnified image of an object placed between its pole and the focus

18] The distance of an object from the focus of a concave mirror of focal length f is x and the distance of the real image from the focus is y. Then

i. (1/x) + (1/y) = (1/f)
ii. (1/x) - (1/y) = (1/f)
iii. xy = f²
iv. None of these

19] The distance of an object from the focus of a convex mirror of focal length f is x and the distance of the image from the focus is y. Then

i. (1/y) - (1/x) = (1/f)
ii. (1/y) + (1/x) = (1/f)
iii. xy = f²
iv. None of these

20] Which of the following statements is correct?

i. The laws of reflection of light hold for plane as well as curved reflecting surfaces
ii. The size of a virtual image can be measured by receiving it on a screen
iii. A dentist uses a convex mirror to examine a small cavity
iv. The focal length of a spherical mirror is half the radius of curvature for all rays

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