Ray optics practice · Mixed difficulty

The magnifying power of a simple microscope is 6. The focal length of its lens in metres will be, if least distance of distinct vision is 25 cm.

A converging lens is used to form an image on a screen. When upper half of the lens is covered by an opaque screen

Assertion : Critical angle is maximum for end colour in water air system for visible light.

Reason: Because $\sin \theta_{\mathrm{C}}=\frac{1}{\mu}$ and $\mu_{\mathrm{r}}$, (refractive index of red colour) is minimum for visible light.

The time taken by sunlight to cross a $5 \mathrm{~mm}$ thick glass plate $(\mu=3 / 2)$ is

A thin double convex lens has radii of curvature each of magnitude $\mathrm{40}\,\,\mathrm{cm}$ and is made of glass with $\mu = 1.65$. The focal length of the lens in nearly

A concave mirror has a focal length $20 \mathrm{~cm}$. The distance between the two positions of the object for which the image size is double of the object size is

Assertion: A concave mirror and convex lens both have the same focal length in air. When they are submerged in water, they will have same focal length.

Reason: The refractive index of water is smaller than the refractive index of air.

A ray of light is incident on the hypotenuse of a right-angled prism after travelling parallel to the base inside the prism. If $\mathrm{\mu }$ is the refractive index of the material of the prism, the maximum value of the base angle for which light is totally reflected from the hypotenuse is

Colour of the sky is blue due to

A glass slab has the left half of refractive index $n_1$, and the right half of $n_2=3 n_1$. The effective refractive index of the whole slab is

A person $\mathrm{6}\,\,\mathrm{feet}$ in length can see his full size erect image in a mirror $\mathrm{2}\,\,\mathrm{feet}$ in length. This mirror has to be

Two convex lenses of focal lengths $\mathrm{0}.\mathrm{03}\,\,\mathrm{m}\,\,{\mkern 1mu} \mathrm{and}\,\,{\mkern 1mu} \mathrm{0}.\mathrm{05}\,\,\mathrm{m}$ are used to make a telescope. The distance kept between the two in order to obtain an image at infinity is

Lux is equal to

A magnifying glass is used as the object to be viewed can be brought closer to the eye than the normal near point. This results in

A person is in a room whose ceiling and two adjacent walls are mirrors. How many images are formed

Relative difference of focal lengths of objective and eye lens in the microscope and telescope is given as

A thin biconvex lens of focal length $20 \mathrm{~cm}$ is made of glass of refractive index 1.5. When it is dipped in a liquid of refractive index $\frac{9}{8}$, it acts as

An achromatic combination of lenses is formed by joining

Find the angle of refraction in a medium $(\mu=2)$ if light is incident in vacuum, making angle equal to twice the critical angle.

A car is moving with at a constant speed of $60 \,{kmh}^{-1}$ on a straight road. Looking at the rear view mirror, the driver finds that the car following him is at distance of $100 {~m}$ and is approaching with a speed of $5 {~km} {~h}^{-1}$. In order to keep track of the car in the rear, the driver begins to glance alternatively at the rear and side mirror of his car after every $2 {~s}$ till the other car overtakes. If the two cars were maintaining their speeds, which of the following statement (s) is/are correct?

The radii of curvature of a double convex lens of glass $(\mu=1.5)$ are in the ratio $1: 2$. This lens renders the rays parallel coming from an illuminated filament at a distance of $6 \mathrm{~cm}$. Calculate the radii of curvature of its surfaces.

For a prism of refractive index $\mathrm{1}\mathrm{.732}$, the angle of minimum deviation is equal to the angle of prism. Then the angle of the prism is

When a picture drawn on paper is seen through a slab of a transparent material of thickness $5\mathrm{~cm}$, it appears to be raised by $1.5 \mathrm{~cm}$. The critical angle at the boundary of this transparent material and air is

Total internal reflection can take place only if

A defective eye cannot see close objects clearly because their image is formed

A glass lens is placed in a medium in which it is found to behave like a glass plate. Refractive index of the medium will be

If in compound microscope ${m_1}$ and ${m_2}$ be the linear magnification of the objective lens and eye lens respectively, then magnifying power of the compound microscope will be

The focal length of objective and eye-piece of a microscope are $\mathrm{1}\,\,\mathrm{cm }\,\mathrm{and}\,\mathrm{ 5}\,\,\mathrm{cm}$ respectively. If the magnifying power for relaxed eye is $45$, then length of the tube is

Monochromatic light is reflected from air into a glass of refractive index $\mu$. The ratio of the wavelength of the incident and refracted waves is

A man is suffering from colour blindness for green colour. To remove this defect, he should use goggles of