Question 1

What is a rainbow? Draw a labelled diagram to show the formation of a rainbow.

Accepted Answer

Rainbow is an arch of colours visible in the sky, caused by the refraction and dispersion of the sun's light by rain or other water droplets in the atmosphere. The colours of the rainbow are generally said to be red, orange, yellow, green, blue, indigo, and violet.Formation :-when a beam of light enters the prism, it gets refracted ans splits into its seven constituent colours. This splitting of light ray occurs because of the different angles  of bending for each other . Hence, each colour passing through the prism bends at different angles with respect to the incident beam.This gives rise to the formation of the colour spectrum.

Question 2

(a) Draw a diagram to show the refraction of light through a glass prism. On this diagram, mark
1. incident ray
2. emergent ray, and
3. angle of deviation.
(b) What is a rainbow? What are the two conditions necessary for the formation of a rainbow in the sky?
(c) What acts as tiny prisms in the formation of a rainbow?
(d) Name the process which is involved in the formation of a rainbow.
(e) What are the seven colours seen in a rainbow?

Accepted Answer

(b) Rainbow is an arch of seven colours visible in the sky which is produced by the dispersion of sun's light by raindrops in the atmosphere. A rainbow is formed in the sky when the sun is shining and it is raining at the same time.(c) Raindrops(d) Dispersion of light(e) Red, Orange, Yellow, Green, Blue, Indigo and Violet.

Question 3

Draw a labeled diagram of rainbow formation. Also, explain the phenomenon of rainbow formation.

Accepted Answer

When sunlight splits due to water drops suspended in air, causing the band of seven colours is called rainbow. Water droplets acts as tiny prism in the sky. The sunlight when enters these tiny droplets undergo internal reflection and also refract these rays which are dispersed causing a band of seven colours called rainbow. Rainbow is always formed in the direction opposite to the sun.

Question 4

Which of the following phenomena of light are involved in the formation of a rainbow?

Accepted Answer

During a formation of a rainbow, the phenomena of dispersion,refraction and internal reflection are involved.A rainbow is a natural spectrum after a shower of rain(every water droplet acts as a small prism) formed due to the dispersion,refraction and internal reflection of different colours.

Question 5

Why do we see a rainbow in the sky only after rainfall?

Accepted Answer

After a shower of rain, rain drops are suspended in air and when a ray of light enters this drop, the drop acts as a prism and splits into its component colors as dispersion takes place. Lights of different colours emerge from the rain drops such as red at the top and violet at the bottom. Thus, a rainbow is formed.

Question 6

Which of the following statements is correct regarding the propagation of light of different colors of white light in air?

Accepted Answer

Air is not a dispersive medium and hence the light of all wavelengths travel with equal velocity.

Question 7

Explain how the formation of rainbow occurs.

Accepted Answer

Formation of Rainbow :(a) The beautiful phenomenon of the rainbow is a combination of three different phenomena - dispersion, refraction and reflection of light.(b) The rainbow appears in the sky after a rain shower.(c) When light rays from the sun enter the water droplets that act like small prisms, they refract and disperse the incident sunlight.(d) This light is then reflected internally, inside the droplet and is finally refracted again.(e) Due to the collective effect of all these phenomena, the seven coloured rainbow 'VIBGYOR' - violet, indigo, blue, green, yellow, orange, red can be seen.

Question 8

How is a rainbow formed?

Accepted Answer

Rainbow can be seen in the sky opposite to the sun just after the rainfall when the water droplets are suspended in the air. The light rays from the sun enter the water droplet and undergo refraction at the surface, then it hits the other end of a droplet and gets internally reflected showing dispersion into seven colors.Hence rainbow formation is the combined phenomena of refraction, internal reflection, and dispersion as shown in figure.

Question 9

Rainbow is formed due to:

Accepted Answer

Hint: The light rays are refracted into the water drop and show total internal reflection and it disperses to show the colors.Step 1: Explaining the concept,The dispersion of light is the splitting of light into the colors and the total internal reflection is defined when the light ray travel in a denser medium towards the rare medium and its fall of the surface at a critical angle then it gets reflected back inside the initial medium.step 2: Conclusion,As the light shows Total internal reflection and dispersion by splitting into the colors in the rainbow. $\textbf{Therefore, option D is the correct answer.}$

Question 10

Which of the following are conditions necessary for observing rainbow?

Accepted Answer

Rainbow occurs due to reflection and refraction occurring from water droplets present in air. So, to see rainbow, it should have rained and the Sun should be present.At the same time, the Sun should be behind the observer. If it is otherwise, only glare of Sun will be felt and no rainbow will be observed.

Rainbow and Scattering

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REVISE WITH CONCEPTS

Formation of Rainbow

Scattering of Light and Tyndall Effect

Colours of the Rainbow are due to Dispersion

QUICK SUMMARY WITH STORIES

Rainbow