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Question
Describe how you could demonstrate that white light is composed of a number of colours.
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Solution
We can show that white light is composed of a number of colours by passing it through a transparent glass prism. A glass prism is a triangular refracting surface. When a beam of white light enters the prism, the light splits, forming a band of seven colours on a screen placed on the other side of the prism. This splitting of light into its constituent colours is called the dispersion of light. The formation of seven colours in a spectrum shows that white light is composed of these seven colours, namely, red, orange, yellow, green, blue, indigo and violet.
RELATED QUESTIONS
A narrow beam PQ of white light is passing through a glass prism ABC as shown in the diagram.
Trace it on your answer sheet and show the path of the emergent beam as observed on the screen DE.
(i) Write the name and cause of the phenomenon observed.
(ii) Where else in nature is this phenomenon observed?
(iii) Based on this observation, state the conclusion which can be drawn about the constituents of white light.
In the following diagram, the path of a ray of light passing through a glass prism is shown:
In this diagram the angle of incidence, the angle of emergence and the angle of deviation respectively are (select the correct option):
(A) X, R and T
(B) Y, Q and T
(C) X, Q and P
(D) Y, Q and P
The path of a ray of light passing through a glass prism is shown below:
In this diagram, the angle of prism, angle of incidence, angle of emergence and angle of deviation, respectively, have been represented by:
(A) O, Y, Z and N,
(B) P, Y, M and Z,
(C) O, X, M and Z,
(D) P, X, Z and N.
State the cause of dispersion of white light
As light rays emerge from a glass prism into air, are they refracted towards or away from the normal?
What is a rainbow?
Which of the following colour of white light has the least wavelength?
(a) red
(b) orange
(c) violet
(d) blue
How does the speed of light determine the optical density of a medium?
A ray of white light falls on a prism. Draw a ray diagram to show that the prism disperses the white light.
The diagram below shows the path taken by a narrow beam of yellow monochromatic light passing through an equiangular glass prism. If the yellow light is replaced by a narrow beam of white light incident at the same angle, draw another diagram to show the passage of white light through the prism and label it to show the effect of prism on the white light.
- A beam of monochromatic light undergoes minimum deviation through an equiangular prism, how does the beam pass through the prism, with respect to its base?
- If white light is used in the same way as in part (a) above, what change do you expect in the emergent beam?
- 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 glass prism for different values of angle of incidence a student would find that the emergent ray:
(A) is parallel to the incident ray
(B) perpendicular to the incident ray
(C) is parallel to the refracted ray
(D) bends at an angle to the direction of incident ray
Draw a labeled ray diagram to illustrate the dispersion of a narrow beam of white light when it passes through a glass prism.
Differentiate between a glass slab and a glass prism.
Which characteristic property of light is responsible for the blue colour of the sky?
Write the range of wavelength of the visible spectrum.
The process of separation of light into its component colours while passing through a medium is called _______.
What is dispersion? Explain in detail.
When white light enters a glass prism from the air, the angle of deviation is least for ____________.
Why do we see a rainbow in the sky only after rainfall?
State the correct sequence (1-7) of colours in the spectrum formed by the prisms A and B, shown in the following figure.
What is Newton’s disc?
Assertion: We can see the rainbow in the sky when the rain starts falling after a spell of bright sunlight.
Reason: The rainbow is formed due to the dispersion of light.
A prism of refractive index `sqrt2` and refracting angle A produces minimum deviation δm of a ray on one face at an angle of incidence 45°, The values of A and δm are, respectively ______.
State True or False:
"Wavelength of red light is close to 700 nm.”
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.
