Ray optics practice · Mixed difficulty

An optical fibre $(\mu=1.72)$ is surrounded by a glass coating $(\mu=1.50)$. Find the critical angle for total internal reflection at the fibre-glass interface.

A monochromatic light wave with wavelength $\lambda_{1}$ and frequency $v_{1}$ in air enters another medium. If the angle of incidence and angle of refraction at the interface are $45^{\circ}$ and $30^{\circ}$ respectively, then the wavelength $\lambda_{2}$ and frequency $v_{2}$ of the refracted wave are:

A medium is said to be dispersive, if

At sun rise or sunset, the sun looks more red than at mid-day because

Convergence of concave mirror can be decreased by dipping in

Nature of image of a real object formed by convex mirror is always

A leaf which contains only green pigments, is illuminated by a laser light of wavelength $0.632\,\,\mu m$. It would appear to be

Image of an object approaching a convex mirror of radius of curvature $\mathrm{20}\,\,\mathrm{m}$ along its optical axis is observed to move from $\frac{{25}}{3}\,\,\mathrm{m}$ to $\frac{{50}}{7}\,\,\mathrm{m}$ in $\mathrm{30 s}$. What is the speed of the object in $\mathrm{kmh}{\,^{ - 1}}$ ?

The velocity of light in glass is $2 \times 10^8 \mathrm{~ms}^{-1}$ and that in air is $3 \times 10^8 \mathrm{~ms}^{-1}$. By how much would an ink dot appear to be raised, when covered by a glass plate $6.0 \mathrm{~cm}$ thick?

Sun light falls normally on a surface of area $36 \mathrm{~cm}^2$ and exerts an average force of $7.2 \times 10^{-9} \mathrm{~N}$ within a time period of 20 minutes. Considering a case of complete absorption, the energy flux of incident light is

A microscope is having objective of focal length $1 \mathrm{~cm}$ and eyepiece of focal length $6 \mathrm{~cm}$. If tube length is $30 \mathrm{~cm}$ and image is formed at the least distance of distinct vision, what is the magnification produced by the microscope. (Take $D=25 \mathrm{~cm}$ )

An object is kept at a distance of $\mathrm{16}\,\,\mathrm{cm}$ from a thin lens and the image formed is real. If the object is kept at a distance of $\mathrm{6}\,\,\mathrm{cm}$ from the same lens, the image formed is virtual. If the sizes of the images formed are equal the focal length of the lens will be

Statement-I: The images formed by total internal reflections are much brighter than those formed by mirrors or lenses.

Statement-II: There is no loss of intensity in total internal reflection.

Which of the following statement is true

The image formed by an objective of a compound microscope is

A ray is incident at an angle of incidence i on one surface of a small angle prism (with angle of prism $\mathrm{A}$) and emerges normally from the opposite surface. If the refractive index of the material of the prism is $\mathrm{\mu }$, then the angle
of incidence is nearly equal to:

The ratio of the refractive index of red light to blue light in air is

A bi-convex lens made of glass (refractive index $\mathrm{1}\mathrm{.5}$) is put in a liquid of refractive index $\mathrm{1}\mathrm{.5}$. Its focal length will

What will be the colour of sky as seen from the earth, if there were no atmosphere

A small telescope has an objective of focal length 140 cm and an eye piece of focal length 5.0 cm. The
magnifying power of telescope for viewing a distant object is:

A nearsighted person cannot clearly see beyond $200 \mathrm{~cm}$. Find out the power of lens needed to see objects at large distances.

A glass prism is kept in air. The angle of deviation is plotted for the different angles of incidence of a monochromatic beam. First we experiment with red colour and then with violet colour.

A person can not see distinctly at the distance less than one metre. Calculate the power of the lens that he should use to read a book at a distance of 25 cm

Statement-A: Minimum deviation for a given prism does not depend on the refractive index $\mu$ of the prism.

Statement-B: Deviation by a prism is given by $\delta=\left(i_1+i_2-A\right)$ and does not have the term $\mu$.

Assertion : A star will appear to twinkle if seen from free space (say moon).

Reason : An air bubble inside water behave like a convergent lens.

Statement-A: Rayleigh scattering is responsible for the bluish appearance of sky.

Statement-B: The sun looks reddish at sunset and sunrise due to rayleigh scattering.

When diffuse reflection from a surface occurs –

If ${I_1}$ and ${I_2}$ be the size of the images respectively for the two positions of lens in the displacement method, then the size of the object is given by

The focal lengths of convex lens for red and blue light are $100\,\,cm$ and $96.8\,\,cm$ respectively. The dispersive power of material of lens is

Refractive index of air is $\mathrm{1}\mathrm{.0003}$. The correct thickness of air column which will have one more wavelength of yellow light ($6000\;\mathop \mathrm{A}\limits^ \circ$) than in the same thickness in vacuum is