Class 8th additional answers and questions from chapter - light

8th class light chapter answer and questions provided me.

 Introduction  

1. Explain the structure and working of a human eye.

Ans - A light-ray from a source passes through cornea and aqueous humour and gets refracted.

The refracted light-ray enters through the eye lens where it is finally refracted by very small amount so as to form a real inverted image on the retina.

The light sensitive cells present in the retina get activated and send electrical signals to the brain.  

Diagram of human eye and it's parts.

                                           

                                                       

2. What is meant by persistence of vision?

Ans - The ability of an eye to continue to see the image of an object for a very short duration after the object has disappeared from view is called persistence of vision.

3. What is night blindness? What causes night blindness?

Ans - Night blindness also called nyctalopia is a defect in the vision in which people cannot view things properly in dim light or at night. It mainly occurs due to the lack of vitamin A in our body.

4. What is spectrum? Explain the phenomenon of dispersion of white light.

Ans - The band of seven colours formed on the paper screen due to the dispersion of white light is called spectrum of white light (VIBGYOR).    

                                         

                                    

The splitting of white light into its constituent seven colours is called dispersion of white light. The dispersion of light into seven colours occurs because the lights of different colours bend through different angles while passing through a glass prism. 

All these colors mixed together and form the white light. However, due to the reflection of light, the seven colors can split and be seen as separate colors rather than a single white light. This phenomenon of the splitting of light into its constituents is called dispersion of light.

5. Differentiate between myopia and hypermetropia.

Ans - The difference between myopia and hypermetropia are : -

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