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प्रश्न
How will you verify the laws of refraction or how the refractive index of glass is determined in the laboratory?
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उत्तर
Place a white sheet of paper on a drawing board. Put a rectangular slab of glass on this white sheet and trace out its boundary ABCD. At any point R on the edge AB, draw a normal NN’. Draw an incident ray PR at any angle say 30°. Fix two pins P1 and P2 vertically on the line PR and at a distance not less than 3 cm from each other. Looking through the other side of the block, fix two pins, P3 and P4 vertically on the white sheet, such that all the four pins P1, P2, P3, and P4 appear to be in a straight line as seen through the glass block. Mark the pinpoints with a fine pencil, remove the block and join the points P3 and P4 by the straight line RS.
PR represents the incident ray and RS represents the refracted ray. ∠PRN and ∠KRN’ are respectively angles of incidence and refraction.
With R as centre and convenient radius, draw a circle cutting the incident ray at Q and the refracted ray at Q’.
From Q and Q’, draw perpendiculars QT and QT’ on the normal NN’
Now sin i = `"QT"/"QR"`
and Sin r = `"Q’T’"/"Q’T’"`
μ = `Sin"i"/Sin"r"="QT"/"QR"."Q’R"/"Q’T’"="QT"/"Q’T’"`
Since QR = Q’R being the radius of the same circle.
Repeat this experiment for other angles of incidence, say 45° and 60°, and find μ.
It is found that for different values of i the ratio.
`sin"i"/Sin"r"` = constant
Thus, it is verified that,
(i) `sin"i"/Sin"r"` is a constant and is equal to aμg.
(ii) The incident the refracted ray and normal line in the same plane.
संबंधित प्रश्न
Why do we get a spectrum of seven colors when white light is dispersed by a prism?
The following diagram shows a 60°, 30°, 90° glass prism of critical angle 42°, Copy the diagram and complete the path of incident ray AB emerging out of the prism marking the angle of incidence on each surface.
Write the relation between the angle of incidence and the angle of refraction for a medium.
Draw diagrams to show the refraction of light from glass to air. In diagram, label the incident ray, refracted ray, the angle of incidence (i) and the angle of refraction (r).
A Water pond appears to be 2.7 m deep. If the refractive index of water is 4/3, find the actual depth of the pond.
After tracing the path of rays of light through a glass slab for three different angles of incidence, a student measured the corresponding values angle of refraction r and angle of emergence e and recorded them in the table given below:
|
S. No. |
∠i |
∠i |
∠e |
|
I |
30° |
20° |
31° |
|
II |
40° |
25° |
40° |
|
III |
50° |
31° |
49° |
The correct observations are:
(A) I and II
(B) II and III
(C) I and III
(D) I, II and III
What is the correct reason for blinking / flickering of stars? Explain it.
a) The blasts in the stars.
b) Absorption of star light by the atmosphere.
c) Motion of the stars.
d) Changing refractive index of gases in the atmosphere.
How does the deviation produced by a prism depend on the wavelength of incident light?
In the diagram alongside a ray of light, PQ is incident normally on one face AB of an equilateral glass prism. What is the angle of incidence at the faces AB and AC?
Calculate the velocity of light in a glass block of refractive index 1.5. (Velocity of light in air = 3 × 108 m/s)
