Ray optics practice · Mixed difficulty

The phenomenon by which light travels in an optical fibres is

Which mirror is to be used to obtain a parallel beam of light from a small lamp?

Assertion: The stars twinkle while the planets do not.

Reason: The stars are much bigger in size than the planets.

If ${\mu _1}\,and\,{\mu _2}$ are the refractive indices of the materials of core and cladding of an optical fibre, then the loss of light due to its leakage can be minimized by having

A parallel beam of light is incident on a converging lens parallel to its principal axis. As one moves away from the lens on the other side of the principal axis, the intensity of light

In a compound microscope cross-wires are fixed at the point

When the convergent nature of a convex lens will be less as compared with air

Angle of minimum deviation for a prism of refractive index $\mathrm{1}\mathrm{.5}$ is equal to the angle of the prism. The angle of the prism is $\left( {\mathrm{given}\,\,\cos \,\,41^\circ \mathrm{\;} - \mathrm{\;}{{24}^\mathrm{'}} - \mathrm{\;}{{36}^{\mathrm{''}}} = \mathrm{\;}0.75} \right)$

When a beam of white light is allowed to pass
through convex lens parallel to principal axis, the
different colours of light converge at different point
on the principle axis after refraction. This is called

If the focal length of the eye piece of a
telescope is doubled, its magnifying power
$(m)$ will be

How should people wearing spectacles work with a microscope

A small source of light is to be suspended directly above the centre of a circular table of radius $R$. What should be the height of the light source above the table so that the intensity of light is maximum at the edges of the table compared to any other height of the source

Light enters from air into a given medium at an angle of $45^{\circ}$ with interface of the air-medium surface. After refraction, the light ray is deviated through an angle of $15^{\circ}$ from its original direction. The refractive index of the medium is

A ray of light is incident at an angle of $60^\circ$ on one face of a prism of angle $30^\circ .$ The emergent ray of light makes an angle of $30^\circ$ with incident ray. The angle made by the emergent ray with second face of prism will be

The communication using optical fibres is based on the principle of

A plano convex lens of $\left( {f = 20\,\,\mathrm{cm}} \right)$ is silvered at plane surface. New $f$ will be

Which of the following is not due to total internal reflection

Assertion: A spherical mirror of focal length ${f}$ in air is used in a medium of refractive index 5 . Then the focal length of mirror in medium becomes octave.

Reason: The radius of curvature of a mirror is double of the focal length.

Four lenses are made from the same type of glass. The radius of curvature of each face is given below. What will have the greatest positive power

An object approaches a convergent lens from the left of the lens with a uniform speed $5 \mathrm{~m} / \mathrm{s}$ and stops at the focus. The image

Frosted glass is widely used for translucent
windows. The region where a transparent
adhesive tape is stuck over the frosted glass
becomes transparent. The most reasonable
explanation for this is

The wavelength of sodium light in air is $5890\,\,{\mathrm{A}^0}$. The velocity of light in air is $3\,\, \times \,\,{10^{ - 8}}\,\,\mathrm{m}{\mathrm{s}^{ - 1}}$. The wavelength of light in a glass of refractive index $\mathrm{1}\mathrm{.6}$ would be close to

A convex mirror is used to form the image of an object. Then which of the following statements is wrong

For a material medium, the values of refractive index for violet and red colours are given as $\mathrm{n}_{\mathrm{v}}=1.56$ and $\mathrm{n}_{\mathrm{r}}=1.44$. The dispersive power of a prism made out of this material is

Two thin lenses when in contact, produce a combination of power $+ \,10\,\,D$. When they are $0.25\,\,m$ apart, the power reduces to $+ \,6\,\,D$. The focal lengths of the lenses (in $m$) are

The light rays from an object have been reflected
towards an observer from a standard flat mirror, the
image observed by the observer are:-

A. Real

B. Erect

C. Smaller in size than object

D. Laterally inverted

Choose the most appropriate answer from the
options given below:

A ray of light is incidenting normally on a plane mirror. The angle of reflection will be

An astronomical telescope in normal adjustment receives light from a distant source $S.$ The tube length is now decreased slightly, then

Relation between critical angles of water and glass is

Statement-I: Different colours of light have same velocity in vacuum, but they have different velocities in in any other transparent medium.

Statement-II: $\nu=c / \mu$, where symbols have standard meanings. For different colours, refractive index, $\mu$ of transparent medium has different values. Therefore, $v$ is different.