Ray Optics and Optical Instruments — Physics STD 12 Science — Question

The radioactive decay of uranium into thorium is expressed by the equation  where ‘X’ is

(a) An electron

(b) A proton

(c) A deuteron

(d) An alpha particle

The plate current in a triode is given by    where I_p, V_p and V_g are the values of plate current, plate voltage and grid voltage, respectively. What are the triode parameters m, r_p and g_m for the operating point at   and  ?

(a) 10, 16.7 kW, 0.6 m mho	(b) 15, 16.7 kW, 0.06 m mho
(c) 20, 6 kW, 16.7 m mho	(d) None of these

The largest wavelength in the ultraviolet region of the hydrogen spectrum is 122nm. The smallest wavelength in the infrared region of the hydrogen spectrum (to the nearest integer) is?

The laws of forces that govern the force between two electric charges were discovered by:

A semiconductor is a material with a small but non-zero band gap that behaves as an insulator at absolute zero but allows thermal excitation of electrons into its ____________ at temperatures that are below its melting point.

Why is gold used in the Gold-leaf electroscope?

Two identical thin rings each of radius R meters are coaxially placed at a distance R meters apart. If Q₁ coulomb and Q₂ coulomb are respectively the charges uniformly spread on the two rings, the work done in moving a charge qfrom the centre of one ring to that of other is

(a) Zero

(b)

(c)

(d)

A solenoid is at potential difference 60 V and current flows through it is 15 ampere, then the resistance of coil will be

(a) 4 Ω

(b) 8 Ω

(c) 0.25 Ω

(d) 2 Ω

In a metal, the separation between conduction band and valence band is of the order:

A paramagnetic material is kept in a magnetic field. The field is increased till the magnetization becomes constant. If the temperature is now decreased, the magnetization