Advertisements
Advertisements
प्रश्न
In an experiment with Foucault's apparatus, the various distances used are as follows:
Distance between the rotating and the fixed mirror = 16 m
Distance between the lens and the rotating mirror = 6 m,
Distance between the source and the lens = 2 m.
When the mirror is rotated at a speed of 356 revolutions per second, the image shifts by 0.7 mm. Calculate the speed of light from these data.
उत्तर
Distance between the rotating and the fixed mirror (R) = 16 m
Distance between the lens and the rotating mirror (b) = 6 m
Distance between the source and the lens (a) = 2 m
Mirror is rotated at a speed of 356 revolutions per second
⇒ ω = 356 rev/s= 356 × 2 π rad/sec
Shift in the image (s) = 0.7 m = 0.7 × 103 m
In Foucault experiment, speed of light is given by \[c = 4 R^2 \frac{wa}{s(R + b)}\]
\[= \frac{4 \times (16 )^2 \times 356 \times 2\pi \times 2}{(0 . 7) \times {10}^{- 3} (16 + 6)}\]
= 2.975 × 108 m/s
Therefore, the required speed of light is 2.975 × 108 m/s.
APPEARS IN
संबंधित प्रश्न
The speed of sound in air is 332 m s−1. Is it advisable to define the length 1 m as the distance travelled by sound in 1/332 s?
In Fizeau method of measuring the speed of light, the toothed wheel is placed in the focal plane of a converging lens. How would the experiment be affected if the wheel is slightly away from the focal plane?
In the original Fizeau method, the light travelled 8.6 km and then returned. What could be the difficulty if this distance is taken as 8.6 m?
What is the advantage of using a polygonal mirror with larger number of faces in Michelson method of measuring the speed of light?
The speeds of red light and yellow light are exactly same
The speed of light is 299, 792, 458 ms−1
(a) with respect to the earth
(b) with respect to the sun
(c) with respect to a train moving on the earth
(d) with respect to a spaceship going in outer space.
Which of the following methods can be used to measure the speed of light in laboratory?
Which of the following methods can be used to measure the speed of light in water?
In an experiment to measure the speed of light by Fizeau's apparatus, following data are used: Distance between the mirrors = 12.0 km,
Number of teeth in the wheel = 180.
Find the minimum angular speed of the wheel for which the image is not seen.
What is the speed of light in a denser medium of polarizing angle 30?
For light incident from air on a slab of refractive index 2, the maximum possible angle of refraction is ______.
An air bubble in glass slab of refractive index 1.5 (near normal incidence) is 5 cm deep when viewed from one surface and 3 cm deep when viewed from the opposite face. The thickness of the slab is,
A small bulb is placed at the bottom of a tank containing water to a depth of 80 cm. What is the area of the surface of water through which light from the bulb can emerge out? Refractive index of water is 1.33. (Consider the bulb to be a point source.)
| A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased further the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light. |
The critical angle for a pair of two media A and B of refractive indices 2.0 and 1.0 respectively is:
| A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased further the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light. |
A point source of light is placed at the bottom of a tank filled with water, of refractive index µ, to a depth d. The area of the surface of water through which light from the source can emerge is:
| A ray of light travels from a denser to a rarer medium. After refraction, it bends away from the normal. When we keep increasing the angle of incidence, the angle of refraction also increases till the refracted ray grazes along the interface of two media. The angle of incidence for which it happens is called critical angle. If the angle of incidence is increased further the ray will not emerge and it will be reflected back in the denser medium. This phenomenon is called total internal reflection of light. |
The critical angle of the pair of a medium and air is 30°. The speed of light in the medium is:
A ray of light travels a distance of 12.0 m in a transparent sheet in 60 ns. The refractive index of the sheet is ______.
