Advertisements
Advertisements
प्रश्न
Describe Fizeau’s method to determine the speed of light.
उत्तर
Speed of light by Fizeau’s method
Apparatus:
- The light from a source S was first allowed to fall on a partially silvered glass plate G kept at an angle of 45°
- It is then allowed to fall on a rotating tooth wheel with N teeth and N cuts of equal widths.
- Light passing through one cut will be reflected by a mirror M kept at a long distanced (about 8 km)
- If the wheel is not rotating, it gets reflected by a partially silvered glass plate.
Working:
- Angular speed of rotation of wheel was increased from zero to GO Until it blocked by an adjacent tooth.
- It is ensured by the disappearance of light while looking partially silvered glass plate.
Expression:
v = `"2d"/"t"`
where, d = distance, t = time taken
angular speed ω = `theta/"t"`
`theta = (2pi)/(2"N") = pi/"N"`
t = `pi/("N"omega)`
v = `(2"dN"omega)/pi = 2.9972 xx 10^8 "ms"^-1`
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?
Consider Galileo's method of measuring the speed of light using two lanterns. To get an accuracy of about 10%, the time taken by the experimenter in closing or opening the shutter should be about one tenth of the time taken by the light in going from one experimenter to the other. Assume that it takes 1/100 second for an experimenter to close or open the shutter. How far should the two experimenters be to get a 10% accuracy? What are the difficulties in having this separation?
Light passes through a closed cylindrical tube containing a gas. If the gas is gradually pumped out, the speed of light inside the tube will
The speeds of red light and yellow light are exactly same
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.
When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index.
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 of wavelength 600 nm propagates from air into a medium. If its wavelength in the medium becomes 400 nm, the refractive index of the medium is ______.
