Advertisements
Advertisements
Question
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.
Advertisements
Solution
Different colours of light bend through different angles with respect to the incident ray as they pass through a prism. The red light bends the least, while the violet bends the most. Thus, the rays of each colour emerge along different paths and thus become distinct. This is the cause of dispersion of white light passing through a glass prism.
Isaac Newton used two glass prims, with one prism in inverted position to show that white light of the Sun contains seven colours. The set-up has been shown below:-
When white light of the Sun passes through the first prism, it gets dispersed into seven colours. When all the seven colours of the spectrum were passed through the second prism, Newton found a beam of white light emerging from the other side of the second prism. This observation gave Newton the idea that the sunlight is made up of seven colours.
RELATED QUESTIONS
Describe an activity to show that colours of white light splitted by a glass prism can be recombined to get white light by another identical glass prism. Also draw ray diagram to show the recombination of the spectrum of white light.
Make two diagrams to explain refraction and dispersion.
Draw a diagram to show the refraction of light through a glass prism. On this diagram, mark
(i) incident ray
(ii) emergent ray, and
(iii) angle of deviation.
Out of the following, the colour of light having the maximum wavelength is:
(a) violet
(b) indigo
(c) green
(d) orange
A ray of white light falls on a prism. Draw a ray diagram to show that the prism disperses 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 the following diagram, the correctly marked angles are
(A) All
(B) Only ∠i and ∠A
(C) ∠i, ∠r and ∠A
(D) ∠i, ∠A and ∠D
Write the range of wavelength of the infrared spectrum.
Observe the given figure and write appropriate phenomenon of light in the box.
The angle of deviation through a prism is minimum when
- Incident rays and emergent rays are symmetric to the prism.
- The refracted ray inside the prism becomes parallel to its base.
- The angle of incidence is equal to that of the angle of emergence.
- When the angle of emergence has doubled the angle of incidence.
Choose the correct answer from the options given below:
