Advertisements
Advertisements
प्रश्न
What is Fresnel’s distance? Obtain the equation for Fresnel’s distance.
Advertisements
उत्तर
- Fresnel’s distance is the distance up to which the ray optics is valid in terms of rectilinear propagation of light.
- Fresnel’s distance is the distance up to which ray optics is obeyed and beyond which ray optics is not obeyed but, wave optics becomes significant.
- From the diffraction equation for first minimum,
sin θ = `lamda/"a"`;
θ = `lambda/"a"` - From the definition of Fresnel’s distance,
sin 2θ = `"a"/"z"`
2θ = `"a"/"z"`
- Equating the above two equation gives,
`lambda/"a" = "a"/(2"z")` - Equating the above two equation gives,
z = `"a"^2/(2lambda)`
APPEARS IN
संबंधित प्रश्न
First diffraction minimum due to a single slit of width 1.0 × 10-5 cm is at 30°. Then wavelength of light used is ______.
What is diffraction?
Differentiate between Fresnel and Fraunhofer diffraction.
Mention the differences between interference and diffraction.
Discuss the special cases on first minimum in Fraunhofer diffraction.
What is resolution?
What is Rayleigh’s criterion?
Discuss diffraction at single slit and obtain the condition for nth minimum.
Discuss the diffraction at a grating and obtain the condition for the mth maximum.
Discuss the experiment to determine the wavelength of monochromatic light using a diffraction grating.
Discuss the experiment to determine the wavelength of different colours using diffraction grating.
Obtain the equation for resolving power of optical instrument
What is the difference between resolution and magnification?
Consider sunlight incident on a slit of width 104 A. The image seen through the slit shall ______.
Consider sunlight incident on a pinhole of width 103A. The image of the pinhole seen on a screen shall be ______.
- a sharp white ring.
- different from a geometrical image.
- a diffused central spot, white in colour.
- diffused coloured region around a sharp central white spot.
