1. Isotopes have the same

Isotopes are atoms of the same element that have the same atomic number (same number of protons) but different mass numbers (different number of neutrons).

2. The main source of solar energy is

The Sun produces energy through nuclear fusion, where hydrogen nuclei fuse to form helium, releasing a tremendous amount of energy in the form of light and heat.

3. Nuclear forces are

Nuclear forces are short-range but spin-dependent, meaning their strength depends on the spin alignment of nucleons (protons and neutrons). They are also charge-independent, acting similarly between proton-proton, neutron-neutron, and proton-neutron pairs.

4. When the speed of electrons increases, then the value of the specific charge on an electron

Due to relativistic effects, as the speed of an electron increases, its relativistic mass increases. Since specific charge is given by 𝑒/𝑚 , an increase in mass leads to a decrease in the specific charge.

5. Nuclear forces are mediated by

Nuclear forces are mediated by mesons, which act as exchange particles between nucleons (protons and neutrons) to hold the atomic nucleus together.

6. An atom bomb is based upon the principle of

An atom bomb is based on the principle of nuclear fission, where a heavy nucleus (like uranium-235 or plutonium-239) splits into smaller nuclei, releasing a huge amount of energy.

7. The first explosion of an atomic device in India was carried out in the state of

The first explosion of an atomic device in India was carried out in the state of (A) Rajasthan at Pokhran on 18 May 1974. It was called "Smiling Buddha."

8. Which of the following will deflect in electric field?

Cathode rays are streams of electrons, which are negatively charged particles. Since they have charge, they get deflected in an electric field. X-rays, gamma (γ) rays, and ultraviolet rays are electromagnetic waves and have no charge, so they do not get deflected in an electric field.

9. Cathode rays can be deflected by

Cathode rays are streams of electrons, which are negatively charged particles. Since they have charge, they can be deflected by both electric and magnetic fields according to Lorentz force principles.

10. After pumping process in laser, ______

In a laser (Light Amplification by Stimulated Emission of Radiation), after the pumping process, a condition called population inversion is achieved. This means that more atoms are in an excited state than in the ground state, which is essential for the stimulated emission of photons and laser action.

11. Chokes used in wireless receiver circuits are called

Chokes used in wireless receiver circuits are designed to block high-frequency AC signals while allowing DC or lower-frequency signals to pass. These chokes are specifically called Radio Frequency (RF) Chokes or High-Frequency Chokes, as they prevent unwanted high-frequency interference in circuits.

12. At resonant frequency of RLC series circuit impedance of the circuit

13. The mutual induction is very large, if the two coils are wound on

Soft iron increases the magnetic flux linkage between the coils, enhancing mutual induction.

14. Copper loss can be minimised by using

Thicker wires reduce electrical resistance, thereby minimizing power loss due to heating in the form of I²R loss (Joule heating).

15. Cores of chokes used in low frequency A.C. circuit are made of

Iron cores are used in chokes for low-frequency AC circuits because they provide high magnetic permeability, which enhances inductance and minimizes energy losses.

16. For long distance power transmission, power lines are made of conducting material like

Aluminium is used for long-distance power transmission because it is lightweight, cost-effective, and has good electrical conductivity. Often, steel-reinforced aluminium conductors (ACSR) are used to provide strength and durability.

17. Power loss can be minimised by transmitting power at

18. The coefficient of mutual induction of two coils is numerically equal to _____ linked with one coil when unit current flows through the neighbouring coil.

The coefficient of mutual induction (M) between two coils is defined as the magnetic flux linked with one coil when unit current flows through the neighboring coil. It is given by: 𝑀 = Φ / 𝐼 ​where Φ is the magnetic flux linked with the coil due to current 𝐼 in the neighboring coil.

19. At resonance, the applied voltage is the potential drop across

At resonance in an RLC series circuit, the inductive reactance (XL) and capacitive reactance (XC) cancel each other out (XL=XC). This means the impedance of the circuit is purely resistive, and the applied voltage appears entirely across the resistor (R).

20. According to quantum theory is emitted in the form of discrete packets of energy called

According to quantum theory, energy is emitted or absorbed in discrete packets called quanta. When referring to light or electromagnetic radiation, these packets are called photons.

21. The electrons will be transmitted

In electron transmission (such as in Transmission Electron Microscopy), electrons pass more easily through less dense (transparent) regions and are scattered or absorbed more in denser portions of the object.

22. Wave theory of light assumed that ______ medium pervaded all space in the universe.

Wave theory of light, as proposed by Huygens, assumed that ether was an invisible, all-pervading medium that filled space and allowed light waves to propagate.

23. The average power of an ac circuit is also called ____ of the circuit.

The average power in an AC circuit is called true power, which is given by P = VI cos(ϕ), where ϕ is the phase angle between voltage and current. It represents the actual power consumed in the circuit.

24. Photon has

A photon is a quantum of electromagnetic radiation that has zero rest mass but carries energy given by E = hν, where h is Planck’s constant and ν is the frequency of the wave.

25. According to special theory of relativity in all frames of reference the laws of physics are

According to Einstein's Special Theory of Relativity, the laws of physics remain the same in all inertial frames of reference, and the speed of light in a vacuum is always constant (approximately 3 × 10⁸ m/s) regardless of the motion of the observer or the source.

26. According to relativity, the length of a rod in motion ____

27. In classical mechanics, the time interval between two events has the same value for all observers irrespective of their

Classical mechanics assumes absolute time, meaning time intervals remain constant for all observers, regardless of motion or position. However, Einstein’s relativity introduced time dilation, where time depends on the observer’s reference frame.

28. The revolving power of a microscope is the _____ distance between two points which can be distinguished.

The resolving power of a microscope is the least distance between two points that can be distinguished.

29. Photoelectric current is

The photoelectric current is directly proportional to the intensity of the incident radiation and the number of photoelectrons emitted per second.

30. In Xenon flash tube, each lasts several

In a Xenon flash tube, the duration of each flash typically lasts a few microseconds to milliseconds, depending on the application and energy input. Fonger-duration flashes, the correct answer: (B) milliseconds (for some applications). For very short-duration flashes, the correct answer (D) microseconds .

31. Canal rays

(A) Affect the photographic plate → Canal rays (positive ions) can expose photographic plates. (B) Are deflected by electric and magnetic fields → Since they are positively charged, they respond to electromagnetic forces. (C) Can produce fluorescence → Canal rays can excite certain materials, causing fluorescence.

32. The strongest force in the nature is

The nuclear force is the strongest fundamental force in nature. It binds protons and neutrons in the atomic nucleus, overcoming electrostatic repulsion. It acts over short distances but is extremely powerful.

33. The wavelength of the matter waves is independent of

The wavelength of matter waves is given by de Broglie's equation: 𝜆 = ℎ / 𝑚𝑣 ​where ℎ is Planck’s constant, 𝑚 is mass, and 𝑣 is velocity. Since charge does not appear in this equation, the wavelength of matter waves is independent of charge.

34. A good moderator should

A good moderator in nuclear reactors should: • Not be a gas (as gases are less efficient in slowing down neutrons). • Not absorb neutrons (as this would reduce the number of available neutrons for fission). • Have a light mass number (to efficiently transfer energy to the neutrons). A good moderator should have all of these properties.

35. The dual nature of light is exhibited by

The dual nature of light refers to the fact that light exhibits both wave-like and particle-like properties. This dual nature is exhibited by phenomena such as: • Diffraction (a wave property) • Photoelectric effect (a particle property)

36. The important conclusion given by Millikan’s experiment about the charge is

The important conclusion given by Millikan’s oil drop experiment was that charge is quantized. The experiment showed that the charge on the oil droplets was always a multiple of a fundamental charge, which is the charge of an electron.

37. The ionisation energy of sodium in KJ per mole is

The ionization energy of sodium (Na) is 496 kJ/mol.

38. In nuclear fission, the percentage of mass converted into energy is about

In nuclear fission, a small fraction of the mass of the nucleus is converted into energy according to Einstein's equation E = mc Sqr , with roughly 0.1% of mass being converted.

39. If alpha, beta and gamma rays carry same momentum, which has the longest wavelength?

ccording to the de Broglie wavelength formula 𝜆 = ℎ / 𝑝 where ℎ is Planck's constant and 𝑝 is momentum, the wavelength is inversely proportional to the momentum. Since alpha, beta, and gamma rays are assumed to have the same momentum in this case, they will indeed have the same wavelength.

40. Curie is a unit of

A curie (Ci) is a unit of radioactivity that measures the number of radioactive decays occurring per second. It is defined as 3.7 × 10¹⁰ decays per second, which corresponds to the radioactivity of 1 gram of radium-226.

41. The fuel used in nuclear power plants is

Uranium-235 (U-235) is the isotope commonly used as fuel in nuclear power plants because it is fissile and can sustain a chain reaction, which is essential for energy production in nuclear reactors.

42. An atomic pile is used for

An atomic pile, also known as a nuclear reactor, is used to conduct nuclear fission. It controls the chain reaction of fissioning uranium or other fissile materials to produce energy.

43. The mass defect per nucleon is called

The mass defect per nucleon is referred to as the packing fraction. It represents the difference between the mass of a nucleus and the total mass of its individual nucleons, divided by the number of nucleons. This value indicates how tightly the nucleus is bound.

44. The fourth state of matter is known as

Plasma is the fourth state of matter, distinct from solid, liquid, and gas. It consists of ionized particles, including free electrons and ions, and is commonly found in stars and lightning.