Practice Questions

Q18.Find the modulation index of an AM wave having 8 V variation where maximum amplitude of the AM wave is 9 V . (1) 0. 8 (2) 0. 5 (3) 0. 2 (4) 0. 1 JEE Main 2022 (29 Jul Shift 1) JEE Main Previous Year Paper

Q18.An unpolarised light beam of intensity 2𝐼0 is passed through a polaroid 𝑃 and then through another polaroid 𝑄 which is oriented in such a way that its passing axis makes an angle of 30° relative to that of 𝑃. The intensity of the emergent light is (1) 𝐼0 (2) 𝐼0 4 2 3𝐼0 3𝐼0 (3) (4) 4 2 JEE Main 2022 (29 Jul Shift 2) JEE Main Previous Year Paper

Q18.Mass numbers of two nuclei are in the ratio of 4: 3. Their nuclear densities will be in the ratio of (1) 4: 3 (2) 3 13 4 (3) 1: 1 (4) 4 13 3

Q18.What is the half-life period of a radioactive material if its activity drops to 1 of its initial value of 30 years ? 16th (1) 9. 5 years (2) 8. 5 years (3) 7. 5 years (4) 10. 5 years JEE Main 2022 (27 Jul Shift 1) JEE Main Previous Year Paper

Q18.Given below are two statements Statement I: In hydrogen atom, the frequency of radiation emitted when an electron jumps from lower energy orbit (E1) to higher energy orbit (E2), is given as hf = E1 −E2 Statement II: The jumping of electron from higher energy orbit (E2) to lower energy orbit (E1) is associated with frequency of radiation given as f = (E2−E1)h . This condition is Bohr's frequency condition. In the light of the above statements, choose the correct answer from the options given below: (1) Both statement I and statement II are true. (2) Both statement I and statement II are false. (3) Statement I is correct but statement II is false. (4) Statement I is incorrect but statement II is true.

Q18.The half life period of a radioactive substance is 60 days. The time taken for 7 th of its original mass to 8 disintegrate will be : (1) 120 days (2) 130 days (3) 180 days (4) 20 days

Q18.The ratio for the speed of the electron in the 3rd orbit of He+ to the speed of the electron in the 3rd orbit of hydrogen atom will be : (1) 1: 1 (2) 1: 2 (3) 4: 1 (4) 2: 1

Q18.Which of the following figure represents the variation of ln with ln𝐴 (if 𝑅= radius of a nucleus and 𝐴= 𝑅0 its mass number) JEE Main 2022 (25 Jun Shift 2) JEE Main Previous Year Paper (1) (2) (3) (4)

Q19.For a transistor to act as a switch, it must be operated in (1) Active region (2) Saturation and cut-off region (3) Cutoff region only (4) Saturated region only

Q19.For a constant collector-emitter voltage of 8 V , the collector current of a transistor reached to the value of 6 mA from 4 mA , whereas base current changed from 20 μA to 25 μA value. If transistor is in active state, small signal current gain (current amplification factor) will be (1) 240 (2) 400 (3) 0. 0025 (4) 200

Q19.The momentum of an electron revolving in 𝑛𝑡ℎ orbit is given by : (Symbols have their usual meanings) (1) 𝑛ℎ (2) 𝑛ℎ 2𝜋𝑟 2𝑟 𝑛ℎ 2𝜋𝑟 (3) (4) 2𝜋 𝑛ℎ

Q19.The maximum and minimum voltage of an amplitude modulated signal are 60 V and 20 V respectively. The percentage modulation index will be (1) 0 . 5% (2) 50% (3) 2% (4) 30% JEE Main 2022 (26 Jul Shift 2) JEE Main Previous Year Paper

Q19.A logic gate circuit has two inputs A and B and output Y . The voltage waveforms of A, B and Y are shown below The logic gate circuit is (1) AND gate (2) OR gate (3) NOR gate (4) NAND gate

Q19.Nucleus A is having mass number 220 and its binding energy per nucleon is 5. 6 MeV . It splits in two fragments B and C of mass numbers 105 and 115 . The binding energy of nucleons in B and C is 6. 4 MeV per nucleon. The energy Q released per fission will be: (1) 0. 8 MeV (2) 275 MeV (3) 220 MeV (4) 176 MeV

Q20.A signal of 100THz frequency can be transmitted with maximum efficiency by (1) Coaxial cable (2) Optical fibre (3) Twisted pair of copper wires (4) Water

Q20.Identify the correct Logic Gate for the following output (Y ) of two inputs A and B . (1) (2) (3) (4)

Q20.A square wave of the modulating signal is shown in the figure. The carrier wave is given by C(t) = 5 sin(8πt) Volt. The modulation index is (1) 0. 2 (2) 0. 1 (3) 0. 3 (4) 0. 4

Q20.In the case of amplitude modulation to avoid distortion the modulation index 𝜇 should be : (1) 𝜇≤1 (2) 𝜇≥1 (3) 𝜇= 2 (4) 𝜇= 0

Q20.Match List-I with List-II List-I List-II (A) Television signal I. 03 KHz (B) Radio signal II. 20 KHz (C) High Quality Music III. 02 MHz (D) Human speech IV. 06 MHz (1) A −I, B −II, C −III, D −IV (2) A −IV, B −III, C −I, D −II (3) A −IV, B −III, C −II, D −I (4) A −I, B −II, C −IV, D −III

Q20.At a particular station, the TV transmission tower has a height of 100 m. To triple its coverage range, height of the tower should be increased to (1) 200 m (2) 300 m (3) 600 m (4) 900 m

Q20.A screw gauge of pitch 0. 5 mm is used to measure the diameter of uniform wire of length 6. 8 cm, the main scale reading is 1. 5 mm and circular scale reading is 7 . The calculated curved surface area of wire to appropriate significant figures is [Screw gauge has 50 divisions on the circular scale] (1) 6. 8 cm2 (2) 3. 4 cm2 (3) 3. 9 cm2 (4) 2. 4 cm2

Q20.Choose the correct statement for amplitude modulation (1) Amplitude of modulating signal is varied in (2) Amplitude of modulated signal is varied in accordance with the information signal. accordance with the information signal. (3) Amplitude of carrier signal is varied in (4) Amplitude of modulated signal is varied in accordance with the information signal. accordance with the modulating signal.

Q20.Amplitude modulated wave is represented by VAM = 10[1 + 0. 4 cos(2π × 104t)] cos(2π × 107t). The total bandwidth of the amplitude modulated wave is (1) 10 kHz (2) 20 MHz (3) 20 kHz (4) 10 MHz

Q20.A FM Broad cast transmitter, using modulating signal of frequency 20 kHz has a deviation ratio of 10 . The Bandwidth required for transmission is : (1) 220 kHz (2) 180 kHz (3) 360 kHz (4) 440 kHz

Q20.In AM modulation, a signal is modulated on a carrier wave such that maximum and minimum amplitude are found to be 6 V and 2 V respectively. The modulation index is (1) 100% (2) 80% (3) 60% (4) 50%