What is the percentage of lead in a lead pencil (in $\%$)?

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 maximum number of possible interference maxima for slit-separation equal to twice the wavelength in Young's double-slit experiment is:

Select the correct pair from the following.

The maximum value of $\sin (\cos (\tan x))$ is

When the angle of inclination of an inclined plane is $\theta$, an object slides down with uniform velocity. If the same object is pushed up with an initial velocity $u$ on the same inclined plane, it goes up the plane and stops at a certain distance on the plane. Thereafter, the body: