Chapter 15 Communication Systems
Chapter 15 Communication Systems Question 1. At which of the following frequency/frequencies the communication will not be reliable for a receiver situated beyond the horizon: (a) 10 kHz (b) 10 MHz (c) 1 GHz (d) 1000 GHz Answer: (b) is correct. Here (c) and (d) frequencies have high penetration power so the earth will absorb them. […]
Chapter 14 Electronics Devices
Chapter 14 Electronics Devices Question 1. In an n-type silicon, which of the following statement is true : (a) Electrons are majority carriers and trivalent atoms are the dopants. (b) Electrons are minority carriers and pentavalent atoms are the dopants. (c) Holes are minority carriers and pentavalent atoms are the doplants. (d) Holes are majority […]
Chapter 13 Nuclei
Chapter 13 Nuclei Question 1. (a) Two stable isotopes of lithium 63Li and 73Li have respective abundance of 7.5% and 92.5%. These isotopes have masses 6.01512 u and 7.01600 u respectively. Find the atomic weight of lithium. (b) Boron has two stable isotopes 105Li and 115Li .Their respective masses are 10.01294 u and 11.00931 u and the atomic weight of boron is 10.811 […]
Chapter 12 Atoms
Chapter 12 Atoms Question 1. Choose the correct alternative from clues given at end of each statement: The size of the atom in Thomson’s model is the atomic size in Rutherford’s model.(much greater than/no different from/much less than.) In the ground state of…………… electrons are in stable equilibrium, while in …………….. electrons always experience a […]
Chapter 11 Dual Nature of Radiation and Matter
Chapter 11 Dual Nature of Radiation and Matter Question 1. Find the (a) maximum frequency, and (b) minimum wavelength of X-rays produced by 30 kV electrons. Answer: Question 2. The work function of caesium metal is 2.14 eV. When light of frequency 6 x 1014 Hz is incident on the metal surface, photo emission of electrons […]
Chapter 10 Wave Optics
Chapter 10 Wave Optics Question 1. Monochromatic light of wavelength 589 nm is incident from air on a water surface. What are the wavelength, frequency and speed of (a) reflected, and (b) refracted light ? Refractive index of water is 1.33. (C.B.S.E. Sample Paper 1991)Answer: (a) For reflected light wavelength is unchanged i. e. X = 589 […]
Chapter 9 Ray Optics and Optical Instruments
Chapter 9 Ray Optics and Optical Instruments Question 1. A small candle 2.5 cm in size is placed 27 cm in front of a concave mirror of a radius of curvature of 36 cm. At what distance from the mirror should a screen be placed in order to receive a sharp image? Describe the nature […]
Chapter 8 Electromagnetic Waves
Chapter 8 Electromagnetic Waves Question 1. Figure shows a capacitor made of two circular plates each of radius 12 cm and separated by 5.0 cm. The capacitor is being charged by an external source (not shown in figure). The charging current is constant and equal to 0.15 A. (a) Calculate the capacitance and the rate […]
Chapter 7 Alternating Current
Chapter 7 Alternating Current Question 1. A 100 Ω resistor is connected to a 220 V, 50 Hz ac supply. (a) What is the rms value of current in the circuit? (b) What is the net power consumed over a full cycle? Answer: Question 2. (a) The peak voltage of an a.c. supply is 300 […]
Chapter 6 Electromagnetic Induction
Chapter 6 Electromagnetic Induction Question 1. Predict the direction of induced current in the situations described by the following Fig. 2(a) to (f). Answer: (a) By Lenz’s law, the face of the coil towards the south pole of the magnet opposes the south pole. So this face should behave as the south pole. Hence the […]