Ray optics practice · Mixed difficulty

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.

An eye can distinguish between two points of an object if they are separated by more than $0.22 \mathrm{~mm}$ when the object is placed at $25 \mathrm{~cm}$ from the eye. The object is now seen by a compound microscope having a $20\,\mathrm{D}$ objective and $10\,\mathrm{D}$ eyepiece separated by a distance of $20 \mathrm{~cm}$. The final image is formed at $25 \mathrm{~cm}$ from the eye. What is the minimum separation between two points of the object which can now be distinguished?

An object is viewed through a compound microscope and appears in focus when it is $\mathrm{5 mm}$ away from the objective lens. When a sheet of transparent material $\mathrm{3 mm}$ thick is placed between the objective and the microscope, the objective lens has to be moved $\mathrm{1 mm}$ to bring the object back into the focus. The refractive index of the transparent material is

Under minimum deviation condition in a prism, if a ray is incident at an angle ${30^ \circ }$, the angle between the emergent ray and the second refracting surface of the prism is

A convex lens of glass $(\mu=1.5)$ having focal length ${f}=15 \mathrm{~cm}$ is dipped completely in water. Focal length of convex lens in water becomes $\left(\mu_{\text {water}}=\frac{4}{3}\right)$

${F_1}$ and ${F_2}$ are focal lengths of objective and eyepiece respectively of the telescope. The angular magnification for the given telescope is equal to

The process not involved in the formation of rainbow is

Statement-A: When a white light is passed through a lens, violet light is more refracted than red light.

Statement-B: Focal length for red light is greated than violet.

Which of the following is not the application infra-red waves: