Lakhmir Singh & Manjit Kaur Test: The Human Eye and the Colourful World- 1


25 Questions MCQ Test NCERT Textbooks (Class 6 to Class 12) | Lakhmir Singh & Manjit Kaur Test: The Human Eye and the Colourful World- 1


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QUESTION: 1

The far point of a healthy person is

Solution:

The near point of the eye is the minimum distance of the object from the eye, which can be seen distinctly without strain. For a normal human eye, this distance is 25 cm.

The far point of the eye is the maximum distance to which the eye can see the objects clearly. The far point of the normal human eye is infinity.

QUESTION: 2

A ray of light travelling in air fall obliquely on the surface of a calm pond. It will-

Solution:

The light ray bends towards the normal as it travels from a rarer medium of air to a denser medium of water, undergoes refraction. Refraction is due to change in speed of light  as it enters from one transparent medium to another. The speed of light increases in rarer medium and decreases in denser medium.

QUESTION: 3

The human eye forms the image of an object at its

Solution:
QUESTION: 4

The far point of a myopic person is 80cm in front of the eye. Which type of lens is required to correct the problem?

Solution:
QUESTION: 5

What Colour we obtain on mixing red green blue ?

Solution:

When red and blue light are combined, the result is magenta. When green and blue light are combined, they make cyan. Red and green light make yellow. And when all three primary colors of light  are combined, we see white light.

QUESTION: 6

The refractive indices of three media P, Q, R, are 1.73, 1.33 and 2.24 respectively. Arrange these media in increasing order of their optical density.

Solution:

C is the correct option.Refractive Index (Index of Refraction) is a value calculated from the ratio of the speed of light in a vacuum to that in a second medium of greater density. In the question the lowest refractive index is of Q (1.33), then P (1.73), and the highest is R (2.24).

QUESTION: 7

The inability among the elderly to see nearby objects clearly because of the weaking of the ciliary muscles is called-

Solution:

Presbyopia is a condition associated with the aging of the eye that results in progressively worsening ability to focus clearly on close objects.

QUESTION: 8

Light waves are

Solution:
QUESTION: 9

The muscles of the iris control the

Solution:

The iris consists of two sheets of smooth muscle with contrary actions : expansion and contraction. These muscle control the size of the pupil and thus determine how much light reaches the sensory tissues of the retina.

QUESTION: 10

At what rate the event should be projected to have the clear image ?

Solution:

When shooting sports the frame rate needs to be much higher than 24. frames per second remember that to slow down footage. it's explosions or cellular division filming for science usually means shooting at a higher framerate more. frames researchers can better study their subject.

QUESTION: 11

What is the least distance for clear vision in old age ?

Solution:

The least distance up to which we can see the objects clearly without any strain is called least distance of distinct vision.In old age least distance is about 25cm.

QUESTION: 12

The phenomena of light responsible for the working of the human eye is       

Solution:

The correct option is Option B.

The phenomenon of light responsible for the working of the human eye is refraction.

QUESTION: 13

The angle through which a ray of light turns on passing through a prism is called-

Solution:
QUESTION: 14

When do we say a person is colour blind ?

Solution:
QUESTION: 15

If an eye has near point at a distance of 0.5m, What is the power of lens required to correct it ?

Solution:

Since the person can't read an object at a distance of 50 cm, therefore focal length must be 0.5 m. We know that ; 
P = 1/f , hence, P = 1/0.5 = 2 dioptre. 

QUESTION: 16

The cause of Astigmatism is

Solution:
QUESTION: 17

The deviation in the path of ray of light can be produced-

Solution:

The bending of light as it passes from one medium to another is called refraction. The angle  and wavelength at which the light enters a substance and the density of that substance determine how much the light is refracted. The bending occurs because light travels more slowly in a denser medium. Hence, by a glass prism as well as a rectangular glass slab.

QUESTION: 18

When a light passes through a prism, it splits into its component colours. This phenomenon is called.

Solution:
QUESTION: 19

What is the observed colour of sky as seen from the moon surface ?

Solution:
QUESTION: 20

What is spectrum-

Solution:
QUESTION: 21

When a person is suffering from both myopia and hypermetropia, what type corrective lens are required-

Solution:
QUESTION: 22

Important defect of vision are-

Solution:
QUESTION: 23

If the person uses spectacles of power + 1.0 Dioptre, What is the nearest distance of distinct vision for him ?

Solution:

∵ Near point = 75 cm and Power of lens = + 1 D
∴    P = 100 / f ( in cm )
f = 100 / P
= 100 / 1
= 100 cm
The distance of distinct vision v can be found as below.
Using lens formula here ,
1/f  = 1/v - 1/u
⇒ 1/v = 1/f + 1/u
= 1 / 100 + 1 / - 75  =  3 - 4 / 300
= - 1 / 300
v = ₋300 cm
=  - 3m  ( in meters)

QUESTION: 24

Ability of the eye lens to adjust its focal length is called

Solution:

The ability of the eye to adjust its focal length is known as accommodation. Since, a nearby object is typically focused at a further distance,the eye accommodates by assuming a lens shape that has shorter focal length.

QUESTION: 25

The approximate focal length of the eye lens when the ciliary muscles are fully relaxed

Solution:

The maximum focal length of eye lens is 2.5 cm.