Advertisements
Advertisements
Question
Explain the construction of plane wavefront using Huygens’ principle.
Advertisements
Solution
a. A plane wavefront is formed when point of observation is very far away from the primary source.
b. Let PQR represent a plane wavefront at any instant. According to Huygens’ principle,all the points on this wavefront will act as secondary sources of light sending out secondary wavelets in the forward direction.
c. Draw hemispheres with P, Q, R…. as centres and ‘ct’ as radius. The surface tangential
to all such hemispheres is P1Q1R1…. at instant ‘t’. It is a new wavefront at time ‘t’.
d. The plane wavefronts is propagated as plane waves in homogeneous isotropic medium.They are parallel to each other.
e. PP1N1, QQ1N2, RR1N3 are the wave normals at P, Q, R respectively. These wave normals show the direction of propagation of plane wavefront.
f. The new wavefront P1Q1R1 is parallel to primary wavefront PQR.
APPEARS IN
RELATED QUESTIONS
On the basis of Huygens' wave theory of light prove that velocity of light in a rarer medium is greater than velocity of light in a denser medium.
Using Huygens's construction of secondary wavelets explain how a diffraction pattern is obtained on a screen due to a narrow slit on which a monochromatic beam of light is incident normally.
What is the shape of the wavefront in the following case?
Light diverging from a point source.
You have learnt in the text how Huygens’ principle leads to the laws of reflection and refraction. Use the same principle to deduce directly that a point object placed in front of a plane mirror produces a virtual image whose distance from the mirror is equal to the object distance from the mirror.
Consider a plane wave front incident on a thin convex lens. Draw a proper diagram to show how the incident wave front traverses through the lens and after refraction focusses on the focal point of the lens, giving the shape of the emergent wave front.
Use Huygens' principle to verify the laws of refraction.
Using Huygens’ principle, verify the laws of reflection at a plane surface.
Use Huygens’s principle to explain the formation of diffraction pattern due to a single slit illuminated by a monochromatic source of light.
When the width of the slit is made double the original width, how would this affect the size and intensity of the central diffraction band?
State Huygens’s principle. Show, with the help of a suitable diagram, how this principle is used to obtain the diffraction pattern by a single slit.
Draw a plot of intensity distribution and explain clearly why the secondary maxima becomes weaker with increasing order (n) of the secondary maxima.
Define the term wavefront. Using Huygen’s wave theory, verify the law of reflection.
Answer the following question.
Define the term wavefront. Using Huygen's wave theory, verify the law of reflection.
A plane wave front AB propagating from denser medium (1) into a rarer medium (2) is incident on the surface P1P2 separating the two media as shown in fig.
Using Huygen’s principle, draw the secondary wavelets and obtain the refracted wave front in the diagram.
According to Huygens principle, ______.
What is the geometrical shape of the wavefront for:
- Light diverging from a point source?
- The pattern of wavefront of the light from a distant star intercepted by earth?
Answer the following question briefly and to the point:
What is the phase difference between any two points lying on the same wavefront?
The inverse square law of intensity is valid for a
Figure shows a standard two slit arrangement with slits S1, S2, P1, P2 are the two minima points on either side of P (Figure). At P2 on the screen, there is a hole and behind P2 is a second 2-slit arrangement with slits S3, S4 and a second screen behind them.
Is Huygen’s principle valid for longitudinal sound waves?
Two light beams of intensities in the ratio of 9 : 4 are allowed to interfere. The ratio of the intensity of maxima and minima ______.
According to Huygens’s principle, the amplitude of secondary wavelets is ______.
How is a wavefront different from a ray?
Using Huygen's wave theory of light, show that the angle of incidence is equal to the angle of reflection. Draw a neat and labelled diagram.
What type of wavefronts are associated with a point source of light?
