Class 10 Science Chapter 11 MCQ

Iris is a flat, colored, ring shaped membrane behind the cornea of the eye. There is a hole in the middle of the Iris which is called pupil of the eye. Therefore, pupil is a hole in the middle of the Iris.

The student sitting on the last bench can read the letters written on the blackboard but is not able to read the letters written in his book because he is suffering from hypermetropia or farsightedness. He can see distant objects clearly but cannot see nearby objects distinctly. Note: Hypermetropia may have blurred vision to a person when looking at objects close to them and clearer vision when looking at objects in the distance.

At noon the sun appears white because the light from the sun is directly overhead and travel relatively shorter distance. The sun appears white as only a little of the blue and violet colours are scattered.

The sky appears blue because some of the blue component of sunlight is scattered by the gas molecules (nitrogen and oxygen) present in the air.

Here, all the statements are correct. Hence, your answer will be option [D].

The cone shaped cells of the retina make us to see colours and also make us distinguish between various colours. Cone cells of the retina function only in bright light. The cones do not function in dim light. This is why when it is getting dark at night, it becomes impossible to see colours of cars on the road.

Here, all the statements are correct. Hence, your answer will be option [D].

The clear sky appears blue is due to Rayleigh scattering of sunlight. The molecules in the air scatter blue light from the sun more than they scatter red light.

As the person has the eye defect, myopia, therefore, a concave lens has to be used whose focal length will be, f = – 2 m (using sign convention). Thus, Power, P = 1/f (where, f is focal length in metre) = 1/- 2 = -0.5 D

As the light from a far-off star comes towards the earth, it bends towards the normal because the air is denser closer to the surface of the earth.

The whole purpose of using a convex lens is to increase the converging power of the eye-lens. The convex lens used in spectacles increase the converging power of islands and helps in forming the image of a nearby object on the retina of the eye.

the propagation of light of different colours of white light in air or vacuum move with the same speed but different wavelengths and frequencies.

Here, all the statements are correct. Hence, your answer will be option [D].

The danger signals installed at the top of tall buildings are red in colour because among all other colours, red colour is scattered the least by smoke of fog. This is primarily because wavelength of red colour is the largest. Thus, it can be easily seen from a distance.

Predators have both the eyes at the front of their heads so that they can judge the distance of their prey accurately.

The reddish appearance of the sun at sunrise or sunset is due to least scattering of red light. The red light has the maximum wavelength. The rays of light have to travel a larger part of the atmosphere.

When the light rays enters the eye through a thin membrane, forms the transparent bulge on the front surface of the eyeball, called the cornea. Most of the refraction for the light rays entering the eye occurs at this outer surface of the cornea.

Here, all the statements are correct. Hence, your answer will be option [D].

The focal length of the eye lens increases when eye muscles relaxed and becomes thinner. The sharp image of the distant object is formed at the retina. This enables us to focus accurately on distant objects.

The seven colours of the spectrum can be denoted by the word VIBGYOR. Where V stands for violet, I for indigo, B for blue, G for green, Y for yellow, O for orange and R for red. Note: These colours in the order of increasing frequency (but decreasing wavelengths) are: red, orange, yellow, green, blue, indigo and violet. Red has the maximum wavelength.

The nitrogen and oxygen gas molecules present in the atmosphere are smaller than the wavelength range of visible light. So, when light coming from the sun hits this very small air molecules, it behaves differently. Since, the different colours of white light have different wavelengths, so they are affected differently. The lower wavelengths lights (blues) are scattered much more by the air molecules but the higher wavelengths lights (reds) are scattered much less.

The thickness of the eye lens is increased to focus the image of a nearby object on the retina of the eye.

The term ‘accommodation’ as applied to the eye refers to its ability to vary the focal length of the lens.

The human eye possesses the power of accommodation to focus on objects at different distances.

The eye lens becomes thicker to focus on nearby objects and thinner to focus on distant objects.