2nd Year Physics Chapter 20 Exercise Solved Questions

Hello dear FSC students, I hope you all are doing great. In today’s tutorial, we will have a look at 2nd Year Physics Chapter 20 Solved Questions. I have started a series of tutorials related to the solution of questions given in 2nd-year physics. In the previous tutorial, I have discussed all the questions of chapter18 with the detailed.

In this post, we will have a detailed look at all the questions given in chapter 20 of FSC physics. I will explain all the questions one by one and give an answer to every question in a simple way. So let’s get started with 2nd Year Physics Chapter 20 Exercise Solved Questions.

2nd Year Physics Chapter 20 Exercise Solved Questions

Question 20.1

• Assumptions of Bohr related to hydrogen atom does not meet the classical physics.

• Bohr says there is no emission of energy when electrons revolve around the nucleus.
• While classical theory says electrons revolving around the nucleus emit energy.

Question 20.2

• When gaseous atom gets energy from the exterior energy source the goes into the excitation state. When de-excite they release photons of energy having a different wavelength.
• These photons of certain wavelength display on the screen in the shape of line these lines are at a specific distance from each other and known as a line spectrum.
• Each element releases the photons of different wavelengths. It shows every element has its different spectrum by these spectrum we can find every element.]

Question 20.3

• In-ground state the hydrogen atom has energy equals to the -13.6eV so atom of hydrogen will get the energy of 13.6eV and get ionized.
• This additional energy of a photon will be absorbed by the electron in the shape of kinetic energy.

Question 20.4

• The energy of H-atom in the ground state is E_O. Other than ground state there are some other levels of energy.
• If an atom of hydrogen is excited after providing energy from an exterior source. The electrons may move to a higher energy level of an atom.
• When the electrons move back to low energy level than ground state it releases energy absorbed during excitation

• Due to that, we have many spectrum lines for a hydrogen atom.

Question 20.5

• Yes, the law of energy conservation works when photons are emitted from an atom.
• When atoms get excitation to the high energy level they absorb energy.
• The amount of energy releases when the atom gets de-energized.

Question 20.6

• Every element release and absorbs radiation of a certain wavelength.
• So different radiation falls on the element but it absorbs only that can emit again.
• So the atom is transparent for radiations of other wavelengths.

Question 20.7

• When energy is provided to the atom from an exterior energy source. Electrons are shifted to high energy state from ground state and in this state atom is said to be in an excited state.

Question 20.8

• X-rays are electromagnetic waves like normal light but their frequency is larger than the normal light.
• So X-rays can reflect, refract, interfere, diffraction and polarized.

Question 20.9

• The light of the laser has high intensity, coherent and single direction.
• The energy of X-ray can be focused at a single point to get the energy used in welding, cutting, and in a surgical instrument, normal light can not be used for these functions.

Question 20.10

• If population inversion does not occur among the energy level of an atom than laser light will not be get.
• The excited atoms in the population inversion state release a large number of coherent photons in a single direction.
• It does not exist without population inversion.

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