Ray optics practice · Medium

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

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

A diminished virtual image can be formed only in

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 aperture of a telescope is made large, because

A person who can see things most clearly at a distance of 10 cm, requires spectacles to enable to see clearly things at a distance of 30 cm. What should be the focal length of the spectacles?

The magnification of an image by a convex lens is positive only when the object is placed

In vacuum the speed of light depends upon

A cut diamond sparkles because of its

Two media having speeds of light $2\,\, \times \,\,{10^8}\mathrm{ m}{\mathrm{s}^{ - 1}}$ and $2.4\,\, \times \,\,{10^8}\,\,\mathrm{m}{\mathrm{s}^{ - 1}}$, are separated by a plane surface. What is the angle for a ray going from medium I to medium II?

Assertion : A beam of white light when passed through a hollow prism, cannot give spectrum.

Reason: Because refractive index of air inside and outside the prism is same, so no refraction and hence no deviation will take place.

Assertion: Blue colour of sky appears due to $s$ cattering of blue colour

Reason: Blue colour has shortest wave length in visible spectrum.

Pick the correct statement from the following

A biconvex lens form a real image of an object placed perpendicular to its principal axis. Suppose the radii of curvature of the lens tend to infinity. Then the image would

A point object is placed at a distance of 10 cm
and its real image is formed at a distance of 20 cm
from a concave mirror. If the object is moved by
0.2 cm away from the mirror, the image will shift
by about

Assertion: A concave mirror of focal length in air is used in a medium of refractive index 2 . Then the focal length of mirror in medium becomes double.

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

Assertion : In modern microscope multicomponent lenses are used for both objective and eye piece.

Reason : Multicomponent lenses increase the magnification.

When light waves suffer reflection at the interface between air and glass, the change of phase of the reflected wave is equal to

Statement-A: Image formed by concave lens is not always virtual.

Statement-B : Image formed by a lens is real if the image is formed in the direction of ray of light with respect to the lens.

The deviation caused in red, yellow and violet colours for crown glass prism are ${2.84^ \circ },\;\,{3.28^ \circ }$ and $3.72^\circ$ respectively. The dispersive power of prism material is

Total internal reflection will the place. When :