Magnetism And Matter — Physics STD 12 Science — Question

The susceptibility of annealed iron at saturation is 5500. Find the permeability of annealed iron at saturation.

1. State the condition under which a large magnification can be achieved in an astronomical telescope.
2. Give two reasons to explain why a reflecting telescope is preferred over a refracting telescope.

If a constant potential difference is applied across a bulb, the current slightly decreases as time passes and then becomes constant. Explain.

If light of wavelength 412.5 nm is incident on each of the metals given below, which ones will show photoelectric emission and why?

Metal	Work Function (eV)
Na	1.92
K	2.15
Ca	3.20
Mo	4.17

The distance between the cathode (filament) and the target in an X-ray tube is 1.5m. If the cutoff wavelength is 30pm, find the electric field between the cathode and the target.

Derive an expression for the resistivity of a good conductor, in terms of the relaxation time of electrons.

Answer the following question:
 virtual image, we always say, cannot be caught on a screen.
Yet when we 'see' a virtual image, we are obviously bringing it on to the 'screen' (i.e., the retina) of our eye. Is there a contradiction?

At noon, the sun and the earth pull the objects on the earth's surface in opposite directions. At midnight the sun and the earth pull these objects in same direction. Is the weight of an object, as measured by a spring balance on the earth's surface, more at midnight as compared to its weight at noon?

1. Write the necessary conditions for the phenomenon of total internal reflection to occur.
2. Write the relation between the refractive index and critical angle for a given pair of optical media.