Ray optics practice · Mixed difficulty

Relation between critical angles of water and glass is

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

Assertion: Diamond glitters brilliantly.
Reason: Diamond does not absorb sunlight.

A thin rod of length $f / 2$ is placed along the principal axis of a concave mirror of focal length $f$, such that its image which is real and elongated, just touches the rod. Then the longitudinal magnification of the rod is

Lux is equal to

Ray optics is valid, when characteristic dimensions are

A convex mirror of radius of curvature $30 {~cm}$ forms an image that is half the size of the object. The object distance is

An astronaut in a spaceship see the outer space as

Which one of the following statements is true

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?

Assertion (A): Speed of light is independent of
its colour only in vacuum.

Reason (R): Red colour light travels slower
than violet colour light in glass.

When sunlight is scattered by atmospheric atoms and molecules, the amount of scattering of light of wavelength $\mathrm{440}\,\,\mathrm{nm}$ is $A$. The amount of scattering for the light of wavelength $\mathrm{660}\,\,\mathrm{nm}$ is approximately

If a biconvex lens of material of refractive index $1.5$ has focal length $20 \mathrm{~cm}$ in air, then its focal length when it is submerged in a medium of refractive index $1.6$ is

A square wire of side 1 cm is placed perpendicular to the principal axis of a concave mirror of focal length 15 cm at a distance of 20 cm. The area enclosed by the image of the wire is

A convex and concave lens of focal length 10 cm and 20 cm respectively are kept in contact with each other. Find focal length of the combination of lens

To obtain the maximum magnification with a simple microscope, where should the eye be placed?

The light gathering power of a camera lens depends on

A convex lens is placed between object and a screen. The size of object is $\mathrm{3}\,\,\mathrm{cm}$ and an image of height $\mathrm{9}\,\,\mathrm{cm}$ is obtained on the screen. When the lens is displaced to a new position, what will be the size of image on the screen?

In a compound microscope the obejctive lens and eye-piece have focal length of $0.95 \mathrm{~cm}$ and $5 \mathrm{~cm}$ respectively, and are kept at a distance of $20 \mathrm{~cm}$. The last image is formed at a distance of $25 \mathrm{~cm}$ from the eye-piece calculate magnifying power:-

A student studying the similarities and differences between a camera and the human eye makes the following observations:

I. Both the eye and the camera have convex lenses.
II. In order to focus, the eye lens expands or contracts while the camera lens moves forward or backward.

III. The camera lens produces upside down real images while the eye lens produces only upright real images.

IV. A screen in camera is equivalent to the retina in the eyes.

V. A camera adjusts the amount of light entering in it by adjusting the aperture of the lens. In the eye, the cornea controls the amount of light.

Which of the above statements are correct?

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

Assertion: An object is placed at a distance of $f$ from a convex mirror of focal length $f$ its image will form at infinity.
Reason: The distance of image in convex mirror can never be infinity.
In above question a statement of assertion is followed by statement of reason mark the correct choice.

Assertion: If the angles of the base of the prism are equal, then in the position of minimum deviation, the refracted ray will pass parallel to the base of prism.

Reason: In the case of minimum deviation, the angle of incidence is equal to the angle of emergence.

If the lower half of a concave mirror’s reflecting surface is made opaque, which of the following statements describe the image of an object placed infront of the mirror

$\mathrm{S1}$: Intensity of the image will increase

$\mathrm{S2}$: The image will show only half of the object

$\mathrm{S3}$: No change in the image

$\mathrm{S4}$: Intensity of the image will be reduced to half

A person suffering from ‘presbyopia’ (myopia and hyper metropia both defects) should use

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

An object is placed at a distance of $10\,\,cm$ from a convex lens of power $5\,\,D$. Find the position of the image

The radius of curvature of a convex mirror is $80 \mathrm{~cm}.$ When a real object is placed at $A$ its image is formed at $B.$ If the size of image is half that of the object, then distance between $A$ and $B$ is

Near and far points of human eye are

Assertion: The refractive index of a prism depends only on the kind of glass of which it is made of and the colour of light.

Reason: The refractive index of a prism depends upon the refracting angle of the prism and the angle of minimum deviation