Light Worksheet-6

Light Worksheet-6

 

  1. What are the uses of kaleidoscope?

 

  1. Define dispersion of light.

 

  1. Give an example of natural dispersion.

 

  1. What is the function of rods and cones in our eye?

 

  1. What is blind spot?

 

  1. What is the function of eyelids.

 

  1. What is the Braille system?

 

  1. What is reflection of light? State the laws of reflection.

 

  1. What are the characteristics of image formed by plane mirror?

 

  1. How will you prove that the angle of incidence is equal to the angle of reflection.

 

  1. Explain the structure and working of human eye.

 

  1. What is Braille system? Explain.

 

Answer:

  1. Designers of wallpapers and fabrics and artists use kaleidoscope to get ideas for new pattern.

 

  1. Spitting of light into its colours is knows as dispersion of light.

 

  1. Rainbow is a natural phenomenon showing dispersion.

 

  1. Cones are sensitive to bright light and colour where as rods are sensitive to dim light.

 

  1. At the junction of the optic nerve and retina, there are no sensory cells, so no vision is possible at the spot. This is called the blind spot.

 

  1. Eyelids prevent any object from entering the eye.

 

  1. Louis Braille developed a system for visually challenged person and published. This is known as Braille system. He developed code for common languages.

 

  1. Reflection is a phenomenon in which a beam of light falls on some surface and returns back in different directions. It may be regular or irregular.

Following are the laws of reflection:

(i) When a ray of light falls on a reflected surface it is reflected in such a way that the angle of incidence is equal to the angle of reflection, i.e. ∠i = ∠r

(ii) The incident ray, the normal and the reflected ray all lie in the same plane.

 

  1. Characteristics of image formed by a plane mirror are:

(i) Plane mirror form virtual images.

(ii) Plane mirror form erect images.

(iii) Image is laterally inverted.

(iv) Image formed is of the same size as the object.

(v) The distance of image from the mirror is equal to the distance of object from the mirror.

 

  1. Draw lines showing the position of the plane mirror, the incident ray and the reflected ray on the paper with the help of your friends.

Remove the mirror. Draw a line making an angle of 90° to the line representing the mirror at the point where the incident ray strikes the mirror. This line is known as the normal.

The angle between the normal and incident ray is called the angle of incidence (∠i).

The angle between the normal and the reflected ray is known as the angle of reflection (∠r). Measure the angle of incidence and the angle of reflection.

Repeat the activity several times by changing the angle of incidence.

Every time the angle of incidence is equal to the angle of reflection.

This proves that the angle of incidence is equal to the angle of reflection.

 

  1. The eye has a roughly spherical shape.

The outer coat of the eye is white. It is tough so that it can protect the interior part of the eyes from any mishap or accident.

Its transparent front part is called cornea.

Behind the cornea, a dark muscular structure called iris.

In the iris, there is a small opening called pupil.

The size of the pupil is controlled by the iris.

The iris controls the amount of light entering the eye.

Behind the pupil of the eye is a lens which is thicker in the centre.

The lens focuses light on the retina.

The retina contains several nerve cells.

Sensations felt by the nerve cells are then transmitted to the brain through the optic nerve. There are two kinds of cells cones and rods.

 

  1. Braille is a method of writing for visually impaired person. This system was invented by Louis Braille in 1821 and adopted in 1932. He was also a blind person.

In this method text is written on a thick paper using special symbols representing the letters of alphabet. Groups of dots are used to write letters.

There is Braille code for common languages, Mathematics and Scientific notation. Braille system has 63 dots patterns.

Each pattern represents a letter, a combination of letters, a common word or a grammatical sign.

Dots are arranged in cells of two vertical rows of three dots each.

Codes of music and mathematics are different. Any language can be read through the codes of Braille.