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.

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

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].

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.

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 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.

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

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 object for the other plane mirror. Number of images formed = 360 degree / x – 1 = 360 / 90 – 1 = 4 – 1 = 3

When the angle between mirrors is 180° then only single image is obtained. If the angle decreases, then the number of images increases. If the angle increases, then the number of images decreases. And when the angle between two plane mirrors become 0 degree, that is, when the two plane mirrors become parallel to each other then, an infinite number of images are formed.

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.

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

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

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.

We can clearly view an object only when image is clearly reflected on retina. Our eyes focus distinct and near objects and reflects the image on retina. When eyes need to focus distinct object, then ciliary muscles reflex which increases the focal length. The eye lens converges the light and the objects are said to be unaccommodated. When eyes need to focus nearby object, then ciliary muscles relax which decreases the focal length. The eye lens diverges the light and the objects are said to be accommodated. The accommodation power of eyes is as close as 25 cm and as far as infinity.

The size of the pupil of the eye is adjusted by “Iris”. The pupil of our eye is an entrance for the light rays to enter our eyes and give us the sensation of sight. If too much light enters our eyes, it can be dangerous for eyes. Whenever the light is strong, the pupil shrinks in order to reduce the entrance of light and protect our eyes. If too less light enters our eyes, we don’t get a clear vision. Whenever the light is weak, the pupil expands in order to increase the entrance of light and improve the vision. This is how pupil of the eye changes its size to adjust for different amount of light.

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].

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