Ray optics practice · Medium

If both the object and image are at infinite distance from a refracting telescope its magnifying power will be equal to

Myopia can be corrected by using the

An object of length $6\,\,cm$ is placed on the principal axis of a concave mirror of focal length $f$ at a distance of $4\,f$. The length of the image will be

The principle used in the transmission of signal through an optical fibre is

To increase the magnifying power of telescope $({f_0} =$ focal length of the objective and ${f_e} =$ focal length of the eye lens)

A hollow prism having refracting angle $60^\circ$ is filled with a liquid having refractive index $\mu .$ If angle of minimum deviation produced by the prism is $30^\circ ,$ then value of $\mu$ will be

Assertion : The minimum distance between a real object and its real image formed by a convex lens is $4 \mathrm{f}$.

Reason : Convex mirror and concave lens form a virtual and erect image for all position of the real object.

The spectrum obtained from a sodium vapour lamp is an example of

Image is formed for the short sighted person at

During a cloudy day, a primary and a secondary rainbow may be created, then the:

What is the power of the spectacles required by a myopic eye whose far point is $50 \mathrm{~cm}$?

The ratio $\frac{\text {real depth}}{\text {apparent depth}}$ is equal to

In the visible region the dispersive powers and the mean angular deviations for crown and flint glass prisms are $\omega ,\,\,\omega '$ and $d,\,\,d'$ respectively. The condition for getting deviation without dispersion when the two prisms are combined is

The focal length of convex lens is 10 cm. Its magnifying power when it is used as a magnifying glass to form the image at (i) near point and (ii) for point is

Deviation of light ray by a thin prism of refractive index $\mu$ and refracting angle $A$ is

Assertion: Two plane mirrors kept at right angles, Deviate any ray of light by $180^{\circ}$ after two reflections.

Reason: The above conditions satisfied only for angle of incidence $i=45^{\circ}$

Assertion: When a convex lens $\left(\mu_g=3 / 2\right)$ of focal length $f$ is dipped in water, its focal length becomes $\frac{4}{3} f$.

Reason: The focal length of convex lens in water becomes $3 f$.

The magnifying power of a microscope decreases when its length is

A spherometer is used to measure

An astronomical refracting telescope is being
used by an observer to observe planets in
normal adjustment. The focal lengths of the
objective and eye piece used in the
construction of the telescope are 20 m and
2 cm respectively. Consider the following
statements about the telescope:
(a) The distance between the objective and
eyepiece is 20.02 m.

(b) The magnification of the telescope is (–) 1000.

(c) The image of the planet is erect and diminished.

(d) The aperture of eye piece is smaller than that of objective.

The correct statements are:

To increase both the resolving power and magnifying power of a telescope

A spectrum is formed by a prism of dispersive power $'\omega '$. If the angle of deviation is $'\delta '$ then the angular dispersion is

In normal adjustment, magnifying power of an astronomical telescope is 6 and length of telescope is $21 \mathrm{~cm}$. The focal length of objective and eye piece are

A plano-convex lens when silvered in the plane side behaves like a concave mirror of focal length $30\,\,cm$. However, when silvered on the convex side it behaves like a concave mirror of focal length $10\,\,cm$. Then the refractive index of its material will be

The optical fibres have an inner core of refractive index ${n_1}$ and a cladding of refractive index ${n_2}$ such that

In reflection over a spherical mirror, ray parallel to principal axis, after reflection from mirror pass through

The minimum distance between the object and its real image for concave mirror of focal length $f$ is

Why sun has elliptical shape on the time when rising and setting? It is due to

Statement-A: If a convex lens of glass is immersed in water its powder decreases.

Statement-B: In water it behaves as a concave lens.

Assertion: Propagation of light through an optical fibre is due to total internal reflection taking place at the core-clade interface.
Reason: Refractive index of the material of the core of the optical fibre is greater than that of air.