# Light Worksheet-8

Light Worksheet-8

1. Name the disease caused by deficiency of vitamin A.

1. What is meant by visually challenged people?

1. What are non-optical aids?

1. What are tactual aids?

1. What is a periscope?

1. If a ray of light falls normally on a mirror, what is angle of reflection?

1. The ray of light that bounces back from a plane mirror.

1. The nature of the image formed by a plane mirror.

1. A devices that is often used as "looking glass".

1. Which kind of spherical mirrors are used in vehicles? Why?

1. Distinguish between real and virtual image.

1. What is the function of the eyelids?

1. Give two uses of periscope.

1. Give some uses of plane mirror.

1. How many plane mirror strips do we use in a kaleidoscope. At what angle are they inclined with respect to each other?

1. Why do we say that the image formed in a plane mirror is "virtual" ?

1. What would you do to see if the barber has cut your hair properly at the back?

1. How many images are formed when two mirrors are placed edge to edge -

(a) At right angles of each other.

(b) At an angle of 60° to each other?

1. (a) How are multiple images formed?

(b) Name a device based on this principle?

1. Give two similarities between a human eye and a camera.

1. Night blindness

1. Visually challenged people have limited vision to see things.

1. Non-optical aids include visual aids, tactual aids, auditory aids and electronic aids.

1. Tactual aids include Braille writer, slate and stylus help the visually challenged persons in taking notes, reading and writing and in learning mathematics.

1. A periscope is a simple device that enables us to see overhead objects that are not directly in the range of our sight.

1. Reflected ray

1. Virtual image

1. Mirror

1. A convex mirror is used in vehicles because it gives the driver a large field of view.

1. Differences:

Real image Virtual image

(a) The rays actually meet at a point.

(b) The image can be obtained on a screen.

(a) The rays do not meet at a point.

(b) The image cannot be obtained on a screen.

1. (a) Eyelids prevent the objects from entering the eye.

(b) They also shut out light when not required.

1. (a) Periscope is used by army men hidden inside the tank to observe the movement of the enemy outside.

(b) It is used in submarines to see the ships on the water surface.

1. Plane mirrors are used for dressing up, shaving beards, in scientific meters and for designing periscope.

1. The kaleidoscope uses a set of three equal size plane mirror strips. The three strips are inclined to each other at angles of 60° each.

1. The image formed in a plane mirror cannot be obtained on a screen. So we, say it is a 'virtual' image.

1. I would keep another mirror parallel to the main mirror in a vertical position.

1. (a) Three images will be formed.

(b) Five images will be formed.

1. (a) When three rectangular strips of plane mirror are kept edge to edge at an angle of 60° to each other, multiple images are formed.

(b) Kaleidoscope is based on this principle.

1. (a) The human eye and camera have a convex lens.

(b) Both form an inverted image of the object.