Chapter – 19
Q.1: How many neutrons and protons do the following nuclei contain?
| Nuclide | Protons | Neutrons |
|---|---|---|
| 13 | ||
| 18 | ||
| 56 | ||
| 82 | ||
| 14 | ||
| 92 |
Q.2: Do , , and gamma rays come from the same element? Why do we find all three in many radioactive samples?
Ans: A radioactive element either emits -particles or -particles, but never both. Gamma radiations generally accompany -emission and, in some cases, with -emission.
Q.1: Explain how you would test whether the radiation from a radioactive source is α, β or Gamma radiation?
Ans: When radiations are allowed to pass through a magnetic field, the α and β particles are deflected while γ-rays pass through undeflected. This technique helps to identify the radiation.
Q.2: A particle which produces more ionization is less penetrating. Why?
Ans: When a particle ionizes an atom, it loses a part of its energy. Since the greater the ionizing power, the greater is the loss of energy; and hence, the smaller is its penetrating power.
Chapter – 19
Q.1: How many neutrons and protons do the following nuclei contain?
| Nuclide | Protons | Neutrons |
|---|---|---|
| 13 | ||
| 18 | ||
| 56 | ||
| 82 | ||
| 14 | ||
| 92 |
Q.2: Do , , and gamma rays come from the same element? Why do we find all three in many radioactive samples?
Ans: A radioactive element either emits -particles or -particles, but never both. Gamma radiations generally accompany -emission and, in some cases, with -emission.
Q.1: The Bohr’s theory of hydrogen atom is based upon several assumptions. Do any of these assumptions contradict classical physics?
Ans: The assumption in Bohr’s theory that an electron moving around the nucleus in a certain orbit does not radiate energy is contrary to classical electrodynamics.
Q.2: Why does the hydrogen gas produced in the laboratory not glow and emit radiations?
Ans: A spectrum is given by the light emitted from an incandescent gas or vapour e.g., electric discharge through a gas or hydrogen-filled discharge tube.
ADVENT OF MODERN PHYSICS
Chapter - 17
Q.1: What do you understand by a frame of reference? What is the difference between inertial frame and non-inertial frame?
Ans: The position and motion of a body can be located with reference to some coordinate system, called the frame of reference.
The frame of reference that is either at rest or moves with uniform velocity is called an inertial frame. It has zero linear or rotational acceleration. Newton’s laws hold well in such a frame. All inertial frames of references are equivalent.
Chapter - 16
Q.1: Under what circumstances does a charge radiate electromagnetic waves?
Ans: A charge radiates electromagnetic (e.m.) waves when it is accelerated.
Q.2: In an electromagnetic wave, what is the relationship, if any, between the variation in the magnetic and electric fields?
Ans: In an electromagnetic wave, the transverse sinusoidal oscillating electric field and magnetic field are propagated at right angles to each other and to the direction of motion.
Chapter - 15
Q.1: What is the function of the concave pole pieces and the coaxial soft iron cylinder in the moving coil galvanometer?
Ans: The concave magnetic poles and the cylindrical core make the magnetic field radial and stronger (so the current becomes directly proportional to the deflection).
Q.2: Why is it necessary to have some form of controlling couple in the moving coil galvanometer?
Ans: Controlling couple is necessary to control the motion of the coil, it is proportional to the current to be measured. It is produced by using a spring control method, which consists of two hair springs attached to a spindle wound in the opposite directions. As the coil rotates the spring winds up and produces a counter torque. The coil comes to rest (the final deflection of the pointer is given) when the deflecting torque (or magnetic torque) is counterbalanced by the controlling torque (or restoring torque).
