Solution

Rutherford's model:
(i)Couldn't explain the stability of atom.
(ii)Couldn't explain the observed line spectra of hydrogen.
Bohr's Atomic Model postulates :
(i) Explained the stability of the nucleus by postulating that the electron can orbit the nucleus in only those special orbits (given by mvr = nh/2pi) in which it does not radiates energy.
(ii) Explained the line spectrum by postulating that the electron emits photons of well-defined unique energies when it undergoes a transition from one permitted orbit to another.

Solution

(a)

Comapring with y=mx+c
m=hc/e
h=me/c
(b)Stopping potential will remain the same because it will not be affected by the increase in distance between the light source and the metal surface A.This is beacause Vo is independent of the intensity of the incident light but depends only upon the frequency or wavelength of the incident light.So increase in the given distance affects only the intensity of the light but not the frequency.

Solution

Suppose the intensity of unpolarized light from the sodium lamp is Io.
(a)Intensity of the polarised light after transmitting from P1 becomes half i.e. Io/2.
(b)When P1 is rotated about the direction of propagation of light then the intensity of transmitted light remains the same.So intensity of the polarised light after transmitting through P2 will become half i.e. Io/2.
OR
Wavefront is the locus of points having the same phase of oscillations.A wavelet is the point of disturbance due to propagation of light . A line perpendicular to wavefront is called ray.

Solution

Solution

We know that width of the central maximum (bright band) of a single slit diffraction experiment is given by 2y=2Dλ/a where a is the width of the slit which implies that width of central maximum is inversely proportional to width of the slit.

Solution

OR

Solution

Radiowaves: These are produced due to oscillating charged particles. The frequency varies from 500 kHz to 1000 MHz.
Uses of radio waves are:
(i)These are used in AM (Amplitude Modulation) from 530 kHz to 1710 kHz.These are also used in ground wave propagation.
(ii)These are used in TV waves ranging from 54 MHz to 890 MHz.
(iii)UHF(Ultra High Frequency) waves are used in cellular phones
Gamma Rays: These rays were discovered by Rutherford and are produced by nuclear decay. They travel with the speed of light and have high penetration power.Frequency ranges from 3 x 10 ^18 Hz to 5 x 10^22 Hz.
Uses of gamma rays:
(i)Used to produce nuclear reaction
(ii)Used in radiotherapy for the treeatment of tumor and cancer.
(iii)Used in food industry to kill pathogenic microorganisms

Solution

(a)Half life of a radioactive element is defined as the time during which half the number of nuclei present initially in the sample of the element decay.

Solution

In an n-type semiconductor, the concentration of electrons is more than that of holes. Similarly in a p-type semiconductor, the concentration of holes is more than that of electrons. During the formation of the p-n junction and due to the concentration gradient across p and n sides holes diffuse from p-side to n-side and electrons diffuse from n-side to p-side.

Solution