Human eye and colourful world

Question 1

Question: The change in focal length of an eye lens to focus the image of objects at varying distances is done by the action of ________.

1.	pupil
2.	ciliary muscles
3.	retina
4.	blind spot

Answer: 2

Question 2

Question: Far point of a normal eye is situated at _________.

1.	25 cm
2.	infinity
3.	50 cm
4.	400 cm

Answer: 2

Question 3

Question: A long-sighted person cannot see objects nearer to his eye than 50 cm. To enable him to read a book 25 cm away, he should use spectacle lenses whose power in dioptres is ____.

1.	-6
2.	-4
3.	-2
4.	+ 4

Answer: 4

Question 4

Question: The process by which a beam of white light splits into its constituent colours is known as _________.

1.	reflection
2.	dispersion
3.	divergence
4.	convergence

Answer: 2

Question 5

Question: The band of colours obtained due to dispersion is known as ______________.

1.	spectrum
2.	rainbow
3.	image
4.	mirage

Answer:

Question 6

Question: Power of a lens is expressed in

1.	dioptre
2.	cm
3.	metre
4.	millimetre

Answer: 1

Question 7

Question: 1 D is the power of a lens of focal length ______ cm.

1.	100
2.	10
3.	1/100
4.	1/10

Answer: 1

Question 8

Question: Hypermetropia is rectified by using

1.	convex lens
2.	concave lens
3.	cylindrical lens
4.	progressive lens

Answer: 1

Question 9

Question: Reciprocal of focal length in metres is known as the ______ of a lens.

1.	focus
2.	power
3.	power of accommodation
4.	far point

Answer: 2

Question 10

Question: The power of a convex lens of focal length 50 cm is ______.

1.	+ 2 D
2.	- 2 D
3.	50 D
4.	- 5 D

Answer: 1

Question 11

Question: Two lenses having powers +2D and -4D respectively are put together. Power of the combination would be

1.	-2 D
2.	+2 D
3.	-4 D
4.	+4 D

Answer: 1

Question 12

Question: The fluid between the retina and the lens is called _______.

1.	aqueous humour
2.	vitreous humour
3.	aqua
4.	humus

Answer: 2

Question 13

Question: Two thin lenses of power +5D and -2D are put in contact with each other. Focal length of the combination is

1.	+3 m
2.	-3 m
3.	0.33 m
4.	-0.33 m

Answer: 3

Question 14

Question: The least distance of distinct vision for infants is _________.

1.	15 cm
2.	20 cm
3.	25 cm
4.	5 cm

Answer: 4

Question 15

Question: The focal length of a lens whose power is -1.5 D is _______.

1.	-66.66 cm
2.	+ 1.5 m
3.	+ 66.66 cm
4.	-1.5 m

Answer: 1