# Dual Nature of Radiation And Matter Questions & Answers with Formulas & NCERT Physics Notes PDF

## Dual Nature of Radiation And Matter Questions & Answers with Formulas & NCERT Physics Notes PDF

In physics or life Dual nature of matter is an important concept for JEE physics Questions and Answers is basically the study of different nature that a matter possesses or exhibits in physics that come from m.sc or b.sc physics. A matter can either display or have a particle nature for a while or wave nature in a variety types of. So let’s learn from us, because we are briefly explaining in Various experiments that have further been conducted to prove this theory below.

1. What is free Electronics in Metal?

These are loosely bound electrons of the atoms, which can move freely within the metal surface but normally cannot leave the metal surface at room temperature.

2.  What is the Emission of Electrons from a metal?

(i) Field Emission: Electrons are emitted on applying a strong electric field.

(ii) Thermionic Emission: Electrons are emitted from the surface of metal when it is properly heated.

(iii) Photoelectric Emission: Electrons are emitted when light radiation of suitable frequency falls on a metal surface.

(iv) Secondary Emission: Electrons are emitted when some highly energetic primary electrons strikes the surface of the metal

3.  What are Photons?

These are the energy particles which are emitted by a source of radiation. They travel in a straight line. The energy of photon is given by E= hc In free space all photons travel with a constant speed of light (3 x 10⁸ms–¹) irrespective of their frequency. Photons travel with different speeds in different media on account of different wavelengths. It is a massless bundle of electromagnetic energy.

4.  What is the Photoelectric Effect?

Photoelectric effect is the phenomenon of emission of electrons from the surface of metal plates when light of a suitable wavelength falls on it. This effect is also exhibited by non-metals and gases. The ejected electrons are called photoelectrons and the current so constituted is called photoelectric current.

5.  What is the Threshold Frequency?

The minimum value of frequency of incident radiation below which the photoelectric emission stops is called threshold frequency. Radiations of frequency higher than threshold frequency only can cause photoelectric effect.

6.  What is the Threshold Wavelength?

The maximum value of wavelength of incident radiation above which the photoelectric emission stops is called threshold wavelength. Radiation of wavelength less than threshold wavelength only can cause photoelectric effect.

7.  What is the Stopping Potential or Cut off Potential?

The retarding potential for which the photoelectric current is just reduced to zero is called cut off

potential, or stopping potential.

8. Laws of Photoelectric Effect (Emission)

(A)  What is the Statement of Emission ?

(1) Law of Intensity: The intensity of photoelectric current is directly proportional to the intensity of incident light.

(2) Law of Energy: The kinetic energy of us emitted photoelectrons increases with increase in energy or frequency of incident light.

(3) Law of Threshold Frequency: For every substance, there is a minimum frequency called threshold frequency. Light of frequency less than that however intense will not be able to affect even a single photoelectron.

9.  What is the Photoelectric Cell ?

A photoelectric cell is a device used for converting light energy into electrical energy. It works on the principle of photoelectric emission. They are of three types

(i) Photo emissive cell

(ii) Photovoltaic cell

(iii) Photoconductive cell.

10.  What is the Dual Nature of matter?

Since radiations have dual nature i.e. it possesses both wave and particle nature and universe is composed of radiations and matter therefore de-broglie conclude that the matter must also possess dual nature.

11.  What are De-Broglie’s conclusions?

(i) A wave is associated with each moving particle whose wavelength is inversely proportional to the mass of the particle and to the velocity of the particle.

(ii) The wavelength associated with a particle at rest is infinite.

(iii) In the case of elementary particles (electrons, 2n protons, neutrons) the wavelength of de-bo broglie waves is comparable with the wavelength of X-rays, hence we mayA experimentally observe their nature.

12.  What is de-Broglie’s hypothesis?

(i) The two physical quantities which govern all the forms of the physical universe are mass and energy.

According to mass-energy relationship

E= mc² where c velocity of light.

(ii) Nature loves symmetry

13.  What is the de-Broglie wavelength?

The waves associated with material particles in motion are called matter or de-Broglie waves and their wavelength is called de-Broglie wavelength.

The de-Broglie wavelength is independent of the charge and nature of the material particle.

14.  What are the Features of PHOTON ?

(i) Energy of photon is given by E=hv= hv/μ

where  h = Planck’s constant,

V = frequency,

c = speed at light,

n = wavelength of light.

(ii)Photons exist only while moving and have zero rest mass.

(iii) The equivalent mass of photon is m = Elc²

(iv) The momentum of photon p= h/Π+E/C

(v) Photons are electrically neutral.

(vi) Photons are not deflected by electric and magnetic fields.

(vii) A photon always travels at the speed of light in vacuum.

(viii) Number of photons is not a conserved quantity.

15.  What is the Work Function?

It is defined as the minimum energy of photon required to pull out electrons from the free surface of the metal.

16.  What are the Uses of photocells:

(i )It is used for reproduction of sound in cinema films.

(ii) It is used as a fire and burglar alarm.

(iii) It is used as automatic switch of street lights

(iv) It is used as a counting machine.

(V) It is used to determine Planck’s constant and

(vi) It is used to measure the temperature of stars and chemical reactions.

(vii) It is used in TV cameras.

(vii) To operate and control electronic devices such as TV and computers etc.

(ix) To control the temperature of furnaces.

(x) In automatic control and checking of traffic signals and speed of automobiles.

(xi) As complexion meters.

(xii) In locating minor flaws or holes in metal sheets.

(xii) In the preparation of solar batteries.

(xiv) In determining the opacity of solids and 4 liquids.

(xv) In meteorology for recording daylight.