The condition for observing Fraunhofer diffraction from a single slit is that the wave front incident on the slit should be ............

In the Fraunhofer diffraction experiment,$L$ is the distance between the screen and the obstacle,$b$ is the size of the obstacle,and $\lambda$ is the wavelength of the incident light. The general condition for the applicability of Fraunhofer diffraction is:

The Fraunhofer spectrum is a

What do the Fraunhofer lines in the solar spectrum indicate?

In Fraunhofer diffraction pattern,slit width is $0.3 \ mm$ and screen is at $1.5 \ m$ away from the lens. If wavelength of light used is $4500 \ Å$,then the distance between the first minimum on either side of the central maximum is [ $\theta$ is small and measured in radian.] (in $mm$)

In Fresnel diffraction,if the distance between the disc and the screen is decreased,the intensity of the central bright spot will