In compound microscope, the focal length and the aperture of the objective used is respectively

A ray of light is incident on a medium of refractive index ' $\mu$ ' at an angle of incidence ' $i$ '. On refraction in the medium ' $\delta$ ' is the angle of deviation. Then

Simple microscope is used to see the object first in blue light and then a red light. Due to the change from blue to red light, its magnifying power

Concave and convex lenses are placed touching each other. The ratio of magnitudes of their power is $2: 3$. The focal length of the system is 30 cm . The focal lengths of individual lens are