Ray Optics Test

Result

Ray Optics Test - 69

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Weekly Quiz Competition

Question 1
4 / -1

A convex and a concave lens separated by distance d are then put in contact. The focal length of thecombination

A
Becomes 0

B
Remains the same

C
Decreases

D
Increases

Solution
Question 2
4 / -1

A thin lens made of glass of refractive index 1.5 has a front surface + 11 D power and back surface – 6 D. If this lens is submerged in a liquid of refractive index 1.6, the resulting power of the lens is

A
– 0.5 D

B
+ 0.5D

C
– 0.625 D

D
+ 0.625 D

Solution
Question 3
4 / -1

An object is placed first at infinity and then at 20 cm from the object side focal plane of the convex lens. The two images thus formed are 5 cm apart. The focal length of the lens is

A
5 cm

B
10 cm

C
15 cm

D
20 cm

Solution
Question 4
4 / -1

The distance between an object and the screen is 100 cm. A lens produces an image on the screen when placed at either of the positions 40 cm apart. The power of the lens is

A
≈ 3 diopters

B
≈ 5 diopters

C
≈ 7 diopters

D
≈ 9 diopters

Solution
Question 5
4 / -1

A convex lens is made of 3 layers of glass of 3 different materials as in the figure. A point object is placed on its axis. The number of images of the object are

A
3

B
4

C
1

D
2

Solution
Question 6
4 / -1

A achromatic combination is made with a lens of focal length f and dispersive power co with a lens having dispersive power of 2co. The focal length of second will be

A
2 f

B
f / 2

C
–f/2

D
–2f

Solution
Question 7
4 / -1

A biconvex lens with equal radii curvature has refractive index 1.6 and focal length 10 cm. Its radiusof curvature will be

A
20 cm

B
16 cm

C
10 cm

D
12 cm

Solution
Question 8
4 / -1

A convex lens

A
Converges light rays

B
Diverges light rays

C
Form real images always

D
Always forms virtual images
Question 9
4 / -1

Two plano-concave lenses (1 and 2) of glass of refractive index 1.5 have radii of curvature 25 cm and 20 cm. They are placed in contact with their curved surface towards each other and the space between them is filled with liquid of refractive index 4/3. Then,the combination is

A
Convex of focal length 70 cm

B
Concave of focal length 70 cm

C
Concave of focal length 66.6 cm

D
Convex of focal length 66.6 cm

Solution
Question 10
4 / -1

Focal length of a converging lens in air is R. If it is dipped in water of refractive index 1.33, then its focal length will be around (Refractive index of lens materials 1.5)

A
R

B
2R

C
4R

D
R/2

Solution