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Question
What is a rainbow?
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Solution
- The rainbow is an arch of seven colours visible in the sky, which is produced by the dispersion of the sun’s light by raindrops in the atmosphere.
- A rainbow is produced by the dispersion of white sunlight by raindrops (or water drops) in the atmosphere. Each raindrop acts as a tiny glass prism, splitting the sunlight into a spectrum.
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RELATED QUESTIONS
State the cause of dispersion of white light passing through a glass prism. How did Newton show that white light of sun contains seven colours using two identical glass prisms. Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the focus of the first prism.
When a ray of light enters a prism, it bends ______ the normal; as it leaves the prism, it bends ______ the normal.
Make two diagrams to explain refraction and dispersion.
A beam of white light falls on a glass prism. The colour of light which undergoes the least bending on passing through the glass prism is:
(a) violet
(b) red
(c) green
(d) blue
Explain briefly, with the help of a neat labelled diagram, how white light gets dispersed by a prism. On which surface of a prism, there is both dispersion and deviation of light, and on which surface of the prism, there is only deviation of light ?
What conclusion do you draw about the nature of white light in part (b)?
In an experiment to trace the path of a ray of light through a triangular glass prism, a student would observe that the emergent ray
(a) is parallel to the incident ray.
(b) is along the same direction of incident ray.
(c) gets deviated and bends towards the thinner part of the prism.
(d) gets deviated and bends towards the thicker part (base) of the prism.
Draw a labeled ray diagram to illustrate the dispersion of a narrow beam of white light when it passes through a glass prism.
Refer to fig
(i) Name the lens L.
(ii) What are the points O, O' called?
(iii) Complete the diagram to form the image of the object AB.
(iv) Write three characteristics of the image.
Differentiate between a glass slab and a glass prism.
What is the cause of the dispersion of white light through a glass prism? Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in an inverted position with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the faces of the prisms.
Write the range of wavelength of the ultraviolet spectrum.
In the diagram, a narrow beam of white light is incident on a right-angled isosceles prism. The critical angle of the material of prism for the yellow colour of white light is 45°. Complete the diagram to show the path of blue, yellow, and red colours of white light till they emerge out of the prism.
Observe the given figure and write appropriate phenomenon of light in the box.
Say TRUE or FALSE
After passing through a prism, white light splits into a band of seven colours
State the correct sequence (1-7) of colours in the spectrum formed by the prisms A and B, shown in the following figure.
State True or False:
"Wavelength of red light is close to 700 nm.”
In the following diagram showing dispersion of white light by a glass prism, the colours 'P' and 'Q’ respectively are:
Make a rainbow
Try to make your own rainbow. You can try this project in the morning or in the evening. Stand with your back towards the Sun. Take a hosepipe or a water pipe used in the garden. Make a fine spray in front of you. You can see different colours of rainbow in the spray.
