In Young's double slit experiment,if one of the slits is closed fully,then in the interference pattern:

Young's double-slit experiment is carried out by using green,red,and blue light,one color at a time. The fringe widths recorded are $\beta_G$,$\beta_R$,and $\beta_B$ respectively. Then:

In the ideal double-slit experiment,when a glass plate (refractive index $\mu = 1.5$) of thickness $t$ is introduced in the path of one of the interfering beams (wavelength $\lambda$),the intensity at the position where the central maximum occurred previously remains unchanged. The minimum thickness of the glass plate is:

Assertion: In Young's double slit experiment,if the wavelength of incident monochromatic light is doubled,the number of bright fringes on the screen will increase.
Reason: The maximum number of bright fringes on the screen is directly proportional to the wavelength of light used.

$A$ beam of electrons is used in $Y.D.S.E.$ The slit width is $d$. When the velocity of the electrons is increased,then:

On using red light $(\lambda = 6600 \ \text{Å})$ in Young's double slit experiment, $60$ fringes are observed in the field of view. If violet light $(\lambda = 4400 \ \text{Å})$ is used, the number of fringes observed will be