Standard 10th Science Experiment 8 Answer Solutions: Verification of the laws of refraction of light Answer Solutions.
Aim :
To measure the angle of incidence, the angle of refraction, the angle of emergence and verify the laws ofrefraction of light.
Requirements :
A rectangular glass slab, a drawing board, a drawing paper, drawing pins, pins, a protractor.
Procedure :
(1) Fix the drawing paper on the drawing board using drawing pins.
(2) Place the rectangular glass slab on it and mark its boundary with a sharp pencil.
(3) Remove the glass slab and draw a normal M1N1 at the point O. Draw a line AO which makes an angleof incidence (i) of 30° with normal M1N1.
(4) Fix pins P1 and P2 on line AO such that the pins are vertical and well separated.
(5) Replace the glass slab properly in its original position.Observe the images of the bases of pins P1 and P2 through the glass slab from the opposite side S2 and fix two pins P3 and P4 such that the bases of these pins are exactly in line with the images of the basesof pins P1 and P2.
(6) Remove pins P3 and P4 and mark their positions by small circles. Draw a line BC through points P3 and P4. Remove pins P1 and P2 and the glass slab. Join OB and draw normal M2N2 at point B.
(7) Measure, the angle of incidence (i),the angle of refraction (r) and the angle of emergence (e).
(8) Repeat the procedure for angles of incidence of 45° and 60°. (9) Find the ratiosin isin r in each case.
Diagram :
Label the various components in the given diagram.
Inferences / Conclusions :
(1) Incident ray AO and emergent ray BC are parallel to each other. The lateral shift is equal to CD.[This shift depends upon the thickness 2 of the glass slab, the refractive index of glass and the angle of [incidence.]
(2) The angle of incidence (i)> the angle of refraction (r). This means when a ray of light travels from air to glass, it bends towards the normal.
(3) The angle of incidence (i) = he angle of emergence (e).
(4) The incident ray and the refracted ray are on the opposite side of the normal to the surface at the point of incidence and all the three i.e., the incident ray , the refracted ray and the normal are in the sameplane.
(5) For a given pair of media, the ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant (Snell’s law ). This constant is called the refractive index of the second medium with respect to the first medium.
Precaution : Pins should be fixed such that they are vertical and well separated
Multiple Choice Questions
•
Choose the correct alternative and write its letter (A), (B), (C), (D) in the box :
Rakesh performs the experiment on tracing the path of a ray of light passing through a rectangular glass slab for different angles of incidence. He observes that in all cases .
(A) i>r but i =e (B) i <r but i =e (C) i >e but i =r (D) i <e but i =r
Answer: A
2. When a ray of light travels from air to glass and strikes the surface of separation at 90° with thesurface, .
(A) it bends towards the normal (B) it bends away from the normal (C) it passes without bending (D) it passes randomly
Answer: C
3. If a ray of light incident from a denser medium passes through a rarer medium in a straight line,the angle of incidence must be .
(A) 0° (B) 30° (C) 60° (D) 90°
Answer: A