In a periscope, the light coming from an object gets reflected ____ times.

The number of images produced by a set of two mirrors depends upon ____.

Which of the following is used in the submarines to see what is happening on the surface of the sea?

How many images of an object placed in between two mirrors is produced when the angle between the mirrors is 90 degrees?

The angle between two mirrors is 0 degrees. How many images would they produce?

The angle which the mirrors in a periscope make with the horizontal is ___ degrees.

A ____ is an optical device that helps us to see over the top of an obstacle.

What should a person  do when dust enters their eyes?

The correct option is c)Wash your eyes using clean water.
Slight temporary visual impairment may occur. Once the dust is removed, the swelling and irritation of the eye is reduced and vision returns to normal. However, there is a possibility of infection due to bacteria contained in dust. Therefore we should immediately wash your eyes with cold water.

An object is perceived to be moving when its images appear at the rate of ___ images per second.

A person enters a dark room. Which cells in the eye would help in vision?

The least distance of distinct vision of a human eye is ___ cm.

What happens to the size of the pupil when a person gets out of the house on a sunny day?

The size of the pupil is controlled by the ___.

Which of the following is good for your eyes?

Which of the following parts of the eye controls the amount of light entering the eye?

Deficiency of vitamin ___ may cause eye problems.