A double convex lens has a focal length of \(25\) cm. The radius of curvature of one of the surfaces is double of the other. What would be the radii if the refractive index of the material of the lens is \(1.5?\)
1. \(100\) cm, \(50\) cm
2. \(25\) cm, \(50\) cm
3. \(18.75\) cm, \(37.5\) cm
4. \(50\) cm, \(100\) cm
A biconvex lens has power \(P.\) It is cut into two symmetrical halves by a plane containing the principal axis. The power of one part will be:
1. | \(0\) | 2. | \(\dfrac{P}{2}\) |
3. | \(\dfrac{P}{4}\) | 4. | \(P\) |
Two similar thin equi-convex lenses, of focal length \(f\) each, are kept coaxially in contact with each other such that the focal length of the combination is \(F_1\). When the space between the two lenses is filled with glycerin which has the same refractive index as that of glass \((\mu = 1.5),\) then the equivalent focal length is \(F_2\). The ratio \(F_1:F_2\) will be:
1. \(3:4\)
2. \(2:1\)
3. \(1:2\)
4. \(2:3\)
1. | \(90^{\circ}\) |
2. | \(180^{\circ}\) |
3. | \(0^{\circ}\) |
4. | equal to the angle of incidence |
Pick the wrong statement in the context with a rainbow.
1. | Rainbow is a combined effect of dispersion, refraction, and reflection of sunlight. |
2. | When the light rays undergo two internal reflections in a water drop, a secondary rainbow is formed. |
3. | The order of colors is reversed in the secondary rainbow. |
4. | An observer can see a rainbow when his front is towards the sun. |
A ray of light is incident at an angle of incidence, \(i\), on one face of a prism of angle A (assumed to be small) and emerges normally from the opposite face. If the refractive index of the prism is \(\mu\), the angle of incidence \(i\), is nearly equal to:
1. \(\mu A\)
2. \(\dfrac{\mu A}{2}\)
3. \(\frac{A}{\mu}\)
4. \(\frac{A}{2\mu}\)
A convex lens A of focal length \(20~\text{cm}\) and a concave lens \(B\) of focal length \(5~\text{cm}\) are kept along the same axis with the distance \(d\) between them. If a parallel beam of light falling on \(A\) leaves \(B\) as a parallel beam, then distance \(d\) in \(\text{cm}\) will be:
1. \(25\)
2. \(15\)
3. \(30\)
4. \(50\)
A plane-convex lens of unknown material and unknown focal length is given. With the help of a spherometer, we can measure the
1. | focal length of the lens. |
2. | radius of curvature of the curved surface. |
3. | aperture of the lens. |
4. | refractive index of the material. |
An object is placed on the principal axis of a concave mirror at a distance of \(1.5f\) (\(f\) is the focal length). The image will be at:
1. | \(-3f\) | 2. | \(1.5f\) |
3. | \(-1.5f\) | 4. | \(3f\) |
If the critical angle for total internal reflection from a medium to vacuum is \(45^{\circ}\), the velocity of light in the medium is:
1. | \(1.5\times10^{8}~\text{m/s}\) | 2. | \(\dfrac{3}{\sqrt{2}}\times10^{8}~\text{m/s}\) |
3. | \(\sqrt{2}\times10^{8}~\text{m/s}\) | 4. | \(3\times10^{8}~\text{m/s}\) |