LIGHT-POST 8

CLASS 8 CHAPTER 16

Light
Day 8

Dear Learners,

In the previous blog, we have learned about applications based on multiple reflection. Let me help you to recall few important points

1.Kaleidoscope and Periscope are based on multiple reflection.
2. Kaleidoscope is based on the formation of multiple images by inclined mirror.
3. Periscope is based on the principle of reflection of light.

Today, we will be learning about Dispersion of Light and formation of rainbow. 

Happy Learning!😊

At the end of it, you will be able to:

1. define spectrum.
2. explain dispersion of light.
3. explain the formation of rainbow.

DISPERSION OF LIGHT

'Dispersion of Light' can be defined as the splitting of white light when it passes through a glass prism into its constituent spectrum of colors (i.e. violet, indigo, blue, green, yellow, orange and red). Dispersion figuratively means 'distribution' and hence that's exactly what is happening in the picture.

The band of seven colour formed on the paper screen due to the dispersion of white light is called Spectrum of White Light. The white light or sunlight is made up of seven colour.

Newton Disc Experiment: https://www.youtube.com/watch?v=pImbN4VwC9E

Sir Issac Newton was the first to obtain the spectrum of sunlight by passing the sunlight through the prism.

Light of all colours travel at the same speed in vacuum. But, in any transparent medium such as glass, water,air, etc, the light of different colour travel with different speeds. The red light travels the fastest and the violet light the slowest of all the seven colours. As the result the rid light bends the least and violet light bends the most.

Click on the link: https://www.youtube.com/watch?v=zx07PShjJmk

FORMATION OF RAINBOW

Rainbows are created when raindrops suspended in the air act as prisms and split the white sunlight incident on them into light’s seven constituent colors. The seven colors – as seen from top to bottom — red, orange, yellow, green, blue, indigo and violet are radiated by the drops as seven contiguous arcs that we collectively call a rainbow.

Rainbow is produced due to the dispersion of white light by small raindrops hanging in the air after rain.

Click on the link: https://www.youtube.com/watch?v=lUjvmgDaKCs

Extra Knowledge: Shape of Rainbow

https://www.youtube.com/watch?v=Ba7nve-pTaM

Double full circle rainbow  https://www.youtube.com/watch?v=oFSSdUhid6Q

More about Rainbow: https://www.youtube.com/watch?v=eEl3G3Ky9Gs

                             

Home Assignment

1. Read page no 256, 257 of your text book.

Answer the questions given below orally -
2. Define spectrum of light.
3. What is dispersion of light?
4. What are the seven colours in a rainbow?
5. How is rainbow formed?
6. Which of the seven colours deviates (a) the least and (b) the most, when white light travels through a prism.