Semiconductor Electronics: Materials, Devices and Simple Circuits — Physics STD 12 Science — Question

Microwaves are electromagnetic waves with frequency in the range of:

The capacity of a condenser is 4   farad and its potential is 100 valts. The energy released on discharging it fully will be

(a) 0.02 Joule

(b) 0.04 Joule

(c) 0.025 Joule

(d) 0.05 Joule

1 atomic mass unit is equal to

(a)  (mass of   molecules)	(b)  (mass of   molecules)
(c)  (mass of one C-atom)	(d)  (mass of  molecules)

The figure here gives the electric field of an EM wave at a certain poiunt and a certain instrant. the wave is transporting energy in the negative z direction. what is tha direction of the magnetic field of the wave at that point and instant.

The first member of the Paschen series in hydrogen spectrum is of wavelength 18,800 Å. The short wavelengths limit of Paschen series is

(a) 1215 Å

(b) 6560 Å

(c) 8225 Å

(d) 12850 Å

Which of the following curves may represent the speed of the electron in a hydrogen atom as a function of the principal quantum number n?

Resistance of one carbon filament and one tungsten lamp are measured individually when the lamp are lit and compared with their respective resistances when cold. Which one of the following statements will be true

(a) Resistance of the carbon filament lamp will increase but that of the tungsten will diminish when hot

(b) Resistance of the tungsten filament lamp will increase but that of carbon will diminish when hot

(c) Resistances of both the lamps will increase when hot

(d) Resistances of both the lamps will decrease when hot

The maximum kinetic energy of a photo electron emitted from a metal is 1.8 eV . The value of stopping potential (cut-off voltage) will be :

A photo cell is a device which: