A Narrow Beam Pq of White Light is Passing Through a Glass Prism Abc as Shown in the Diagram. - Science


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.



(i) Dispersion of light

Cause: The dispersion of white light occurs because colors of white light travel at different speeds through glass prism. Different colours undergo different deviations on passing through prism.

(ii) Rainbow is the example of dispersion of light observed in nature.

It is caused due to dispersion of sunlight by water droplets in the atmosphere. It always forms in the direction opposite to the sun.

(iii) White light is a mixture of seven colours. The sequence of colours given by the prism is Violet, Indigo, Blue, Green, Yellow, Orange and Red. VIBGYOR is the acronym for this sequence. The red light bends the least and violet light bends the most.

Concept: Dispersion of Light Through Prism and Formation of Spectrum
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2013-2014 (March) All India Set 3


Study the following figure in which a student has marked the angle of incidence (∠i), angle of refraction (∠r), angle of emergence (∠e), angle of prism (∠A) and the angle of deviation (∠D). The correctly marked angles are

(a) ∠A and ∠i

(b) ∠A, ∠i and ∠r

(c) ∠A, ∠i, ∠e and ∠D

(d) ∠A, ∠i, ∠r and ∠D

Study the following ray diagram:

In this diagram, the angle of incidence, the angle of emergence and the angle of deviation respectively have been represented by

(A) y, p, z

(B) x, q, z

(C) p, y, z

(D) p, z, y

 What will happen if another similar glass prism is placed upside down behind the first prism?

Which is refracted most by a prism : red light or violet light? Explain why?

The colour of white light which is deviated the maximum on passing through the glass prism is:
(a) blue
(b) indigo
(c) red
(d) orange

Which of the following colour of white light has the least wavelength?
(a) red
(b) orange
(c) violet
(d) blue

When white light passes through a prism, it ............

The speed of light in air or vacuum is

A ray of light moving from an optically rarer to a denser medium

The seven colours in the spectrum of sunlight in order, are represented as :

State the speed of light in (a) air, (b) water, and (c) glass

Which is optically denser: water or air? Give reason

Out of air and glass, which is optically rarer? Give reason.

A ray of white light falls on a prism. Draw a ray diagram to show that the prism disperses the white light.

In figure AO is the ray of white light falling on a prism PQR. Complete the diagram till the light emerges out from the prism and falls on the screen.

What do you understand by the term spectrum? Name the various colours present in the spectrum of sunlight.

What do you understand by the term spectrum?

In which of the following four diagrams is the correct path of a ray of light passing through a glass prism shown ?

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

What do you understand by the term spectrum?

What do you mean by spectrum?

A wave has wavelength 50Å of name the wave.

A wave has wavelength 50Å of State its one use.

Name the waves of lowest wavelength.

A Beam of Blue, Green, and Yellow Light Passes Through The Earth's Atmosphere. Name the Colour Which is Scattered the Least.

The phenomenon of splitting of light into its component colours is ___________ .

Draw a labelled diagram: Dispersion of light through a prism.

Answer the following:

What do you mean by dispersion? Name the different colours of light in the proper sequence in the spectrum of light. 

How can the presence of infrared Radiations be detected?

Write the range of wavelength of the visible spectrum.

Write the range of wavelength of the ultraviolet spectrum.

Match the Columns:

Column ‘A’ Column ‘B’
The wavelength of red light (a) 600 nm
(b) 700 nm
(c) 500 nm

The process of separation of light into its component colours while passing through a medium is called _______.

Write an Explanation.

Critical angle

Draw a neat and labelled diagram for dispersion of light.

Rainbow is a beautiful natural phenomenon. It is the combined effect of a natural three processes together produced by light. Write it into the circle.

Observe the given figure and write appropriate phenomenon of light in the box.

Observe the given figure and answer the following questions.

  1. Which colour light rays bend most?
  2. Which colour light rays bend least.
  3. What is the wavelength of violet light rays?

The splitting of white light in to seven colors is called ______.

The sunlight can be split into its constituent colors using ______.


Rainbow is formed by dispersion of which light by water drops


After passing through a prism, white light splits into a band of seven colours

What is dispersion? Explain in detail.

Define dispersion of light.

State the correct sequence (1-7) of colours in the spectrum formed by the prisms A and B, shown in Figure 15.2.

Which one of the following is involved for the formation of rainbow in the sky? 

What is Newton’s disc?

In dispersion, the color of light that will bend more is ______.

The periscope is an optical device with a polished surface that reflects the light falling on it.

Curved mirrors have surfaces that are spherical, cylindrical, parabolic, and ellipsoid.

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.

What is a rainbow?

During dispersion of white light by prism placed in air, for a particular value of angle of prism,

______ colour is deviated the least in the spectrum of white light obtained with a glass prism.

The angle of deviation through a prism is minimum when

  1. Incident rays and emergent rays are symmetric to the prism.
  2. The refracted ray inside the prism becomes parallel to its base.
  3. The angle of incidence is equal to that of the angle of emergence.
  4. When the angle of emergence has doubled the angle of incidence.

Choose the correct answer from the options given below:

The dispersive powers of flint glass and crown glass are 0.053 and 0.034, respectively and their mean refractive indices are 1.68 and 1.53 for white light. Calculate the angle of the flint glass prism required to form an achromatic combination with a crown glass prism of refracting angle 4°:

dispersive power of crown glass? Given that µv = 1.5230, µr = 1.5145

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.”

In the following diagram showing dispersion of white light by a glass prism, the colours 'P' and 'Q’ respectively are:  

State the colour which bends:

  1. The most.
  2. The least while passing through a glass prism.

Observe the given diagram and answer the questions.

  1. Name the process shown in the figure.
  2. Name the colour that deviates the most.
  3. Name the colour that deviates the least.
  4. Name any one phenomenon in nature which is based on the above process.
  5. Define ‘spectrum’.


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