A convex lens whose refractive index is $n_2$, immersed in a liquid whose refractive index is $n_1,\left(n_2>n_1\right)$. What will be the difference in the working style?
If several lenses of focal lengths $f_1, f_2, f_3 \ldots$ are kept in contact with each other, then what will be the effective focal length of this combination?
Answer
$\frac{1}{f}=\frac{1}{f_1}+\frac{1}{f_2}+\frac{1}{f_3}$In terms of power, $P = P _1+ P _2+ P _3+\ldots .$.
A convex lens with a refractive index is placed in that medium whose refractive index is equal to the refractive index of the lens. What will be the focal length of the lens in this medium?
Answer
In this condition the lens will behave like a plane glass plate, hence its focal length will be infinite.
Write any two conditions for total internal reflection.
Answer
(i) Light should move from denser medium to rarer medium. (ii) The value of angle of incidence should be greater than the critical angle in the given medium.
The angle of incidence formed in the dense medium for which the angle of refraction formed in the rarer medium, is at right angle i.e. $90^{\circ}$, is called the critical angle for the interface of both the medium.
(i) The incident ray, reflected ray and normal ray lie in the same plane. (ii) In regular reflection the angle of incidence $\angle i$ is always equal to the angle of reflection $\angle r$.
When a ray is incident on a surface and when it returns back to the medium, this phenomenon is called reflection. A densely polished surface or mirror reflects light.
"A microscope and a telescope should have high magnification power as well as adequate resolution power." Explain the meaning of the statement.
Answer
If the magnification power is high then the object appears larger and clearly, but if the resolution power is low then its structure cannot be seen clearly.
The magnifying power of a simple microscope will be maximum for which colour of light and minimum for which colour of light?
Answer
Since $f_{ v }< f_{ R }$. Hence, from the formula $m =$ $\left(1+\frac{ D }{f}\right)$ it is clear that the magnifying power will be maximum for violet colour and minimum for red colour.