Class 8 Science Chapter 13 MCQ

The point at which the incident ray strikes the mirror is called the point of incidence. The angle of reflection is always equal to the angle of incidence.

Iris is a dark muscular structure behind the cornea, which controls the amount of light entering into the eye.

The image formed by a plane mirror is virtual or unreal and it is also created behind the mirror. The image formed in a plane mirror is the same distance behind the mirror and the same size as the object as the object in front of it. And the image formed by a plane mirror is erect and always laterally inverted.

We can see a non-luminous object (object that does not produce its own light), when the light reflected by the object enters our eyes.

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

The farthest point on the eye at which an object can be seen clearly is known as the “far point” of the eye. The nearest point up to which the eye can see an object clearly without any strain, is called the near point of the eye. The near point of a normal human eye is at a distance of 25 cm from the eye. This means, the most comfortable distance at which one can read a book with normal eyes is about 25 cm from the eyes.

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

Cones are sensitive to bright light and they sense color. However, rods are sensitive dim light.

We know that a plane mirror forms only a single image of an object placed in front of it. When two plane mirrors are kept inclined at an angle, they can form multiple images of an object. This is because the image of an object formed in one plane mirror acts as a object for the other plane mirror. Number of images formed = 360 degree / x – 1

The image formed by a plane mirror is virtual or unreal and it is also created behind the mirror. The image formed in a plane mirror is the same distance behind the mirror and the same size as the object as the object in front of it. And the image formed by a plane mirror is erect and always laterally inverted.

The objects which do not emit their own light are called “non luminous” objects. Actually, the moon the non-luminous objects cannot make their own light. The moon, earth, table, chair, book, trees, plants, flowers, human beings, mirror, diamond are some of the examples of non-luminous objects.

A periscope works on the reflection of light from two plane mirrors arranged parallel to one another. It is an optical device. The principal followed in this device is reflection of light between two mirrors which are parallel to each other. Light from object incidence on the mirror and reflected to the mirror which is parallel to earlier mirror. The reflection from the latter mirror is reflected to eyes. This device is used to view the objects which are not in eyesight level. This device is majorly used in submarines and in army bunker.

The deficiency of one of the following in the diet of a person for a considerable time can lead to a disease called night blindness. This one is “Vitamin A”. The impaired dark adaptation of eyes is called as night blindness. People with this impairment can hardly see in dim environment or during night time. This due to vitamin deficiency is mostly treatable with vitamin supplement. Vitamin A helps in transfer of nerve impulses into image to retina. Some of the food with Vitamin A are eggs, cod liver oil, yellow and orange fruits and vegetables and so on.

Auditory nerve is not a part of the human eye. Explanation: Auditory nerve is a nerve bundle that transmits sound from cochlea to the brain. Cochlea is a auditory sense organ found at the back of each ears.

The shape of the lens is changed by ciliary muscles so that the image forms at a sharp focus at the retina. The lens becomes thicker to focus at near objects and becomes thinner to focus at distant objects.

According to the law of reflection, the angle of incidence is equal to the angle of reflection. If the incident ray makes an angle of 65 degree with the surface of plane mirror, than the angle of incidence can be calculated as: Angle of incidence = 90 – angle made with the plane mirror = 90 – 65 = 25 degree. Since, the angle of incidence is equal to the angle of reflection, therefore the required angle of reflection = 25 degree

Screen in a cinema hall produces diffuse reflection of light. When light incidence on smooth surface, the light is reflected in one direction as parallel beam. This is why our eyes cannot view the reflection from mirror, water and polished wood directly. When the light incidence on rough surface, the light is reflected in many directions. So, in cinema hall, the screen is designed as rough and irregular surface. In theatre, the projector projects parallel light rays which falls on screen. Due to irregularity of screen, the light is reflected in different direction. This type of reflection helps people from anywhere in the theatre to see the picture projected by the projector

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

In the human eye, when the light rays enter to a sharp focusing point on the retina. It acts as the film on camera. It receives the image and passes to cornea. Here, the internal lens of the eyes is focused by cornea. It transforms this image falling on the lens into electrical impulses. The electrical impulses are transferred to optic nerves which carry information to brain and we can see the object.

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

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

The medical condition in which the lens of eye of a person becomes progressively cloudy resulting in blurred vision is called cataract. Cataract develops when the eye-lens of a person becomes cloudy or even opaque due to the formation of a membrane over it. Cataract decreases the vision of eye gradually. The vision of the person can be restored after getting surgery done on the having cataract. The eye defect called cataract cannot be corrected by any type of spectacle lenses.

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

The impression or sensation remains on the retina for about 1/16th of a second even after removal of the object.

Reflection is bouncing back of light rays from the surface of an object.