Practice Questions

Q23.Match List I and List II List I List II A Microwaves I Physiotherapy B UV rays II Treatment of cancer JEE Main 2023 (31 Jan Shift 2) JEE Main Previous Year Paper C Infra-red rays III Lasik eye surgery D X-rays IV Aircraft navigation Choose the correct answer from the option given below: (1) A-II, B-IV, C-III, D-I (2) A-IV, B-I, C-II, D-III (3) A-IV, B-III, C-I, D-II (4) A-III, B-II, C-I, D-IV

Q23.Two plates A and B have thermal conductivities 84 W m-1 K-1 and 126 W m-1 K-1 respectively. They have same surface area and same thickness. They are placed in contact along their surfaces. If the temperatures of the outer surfaces of A and B are kept at 100∘C and 0∘C respectively, then the temperature of the surface of contact in steady state is_____ ∘C.

Q23.Figure below shows a liquid being pushed out of the tube by a piston having area of cross section 2 . 0 cm2. The area of cross section at the outlet is 10 mm2. If the piston is pushed at a speed of 4 cm s-1, the speed of outgoing fluid is _____ cm s-1

Q23.Given below are two statements : Statement I : Electromagnetic waves are not deflected by electric and magnetic field. Statement II : The amplitude of electric field and the magnetic field in electromagnetic waves are related to . each other as E0 = √μ0ε0 B0 In the light of the above statements, choose the correct answer from the options given below: (1) Statement I is true but statement II is false (2) Both Statement I and Statement II are true (3) Statement I is false but statement II is true (4) Both Statement I and Statement II are false

Q24.In a Young’s double slit experiment, the intensities at two points, for the path difference λ and λ ( λ being the 4 3 wavelength of light used) are I1 and I2 respectively. If I0 denotes the intensity produced by each one of the individual slits, then I1+I2 = ______ . I0

Q24.The amplitude of a particle executing SHM is 3 cm. The displacement at which its kinetic energy will be 25% more than the potential energy is: ______ cm.

Q24.A transverse harmonic wave on a string is given by 𝑦𝑥, 𝑡= 5 sin6𝑡+ 0 . 003𝑥 where 𝑥 and 𝑦 are in cm and 𝑡 in sec. The wave velocity is _________ m s-1.

Q24.A ray of light is incident from air on a glass plate having thickness √3 cm and refractive index √2 . The angle of incidence of a ray is equal to the critical angle for glass-air interface. The lateral displacement of the ray when it passes through the plate is ____ × 10−2 cm . (given sin 15°= 0. 26 )

Q24.In a reflecting telescope, a secondary mirror is used to: (1) reduce the problem of mechanical support (2) make chromatic aberration zero (3) move the eyepiece outside the telescopic tube (4) remove spherical aberration

Q24.Two transparent media having refractive indices 1. 0 and 1. 5 are separated by a spherical refracting surface of radius of curvature 30 cm. The centre of curvature of surface is towards denser medium and a point object is placed on the principal axis in rarer medium at a distance of 15 cm from the pole of the surface. The distance of image from the pole of the surface is cm.

Q24.A rectangular block of mass 5 kg attached to a horizontal spiral spring executes simple harmonic motion of amplitude 1 m and time period 3 . 14 s. The maximum force exerted by spring on block is ___ N.

Q24.As shown in figures, three identical polaroids P1 , P2 and P3 are placed one after another. The pass axis of P2 and P3 are inclined at angle of 60º and 90º with respect to axis of P1 . The source S has an intensity of 256 W m−2 . The intensity of light at point O is _____ W m−2 . ∘

Q24.A fish rising vertically upward with a uniform velocity of 8 m s–1, observes that a bird is diving vertically downward towards the fish with the velocity of 12 m s–1. If the refractive index of water is 34 , then the actual velocity of the diving bird to pick the fish, will be __________m s−1.

Q24.The fundamental frequency of vibration of a string between two rigid support is 50 Hz. The mass of the string is 18 g and its linear mass density is 20 g m−1 . The speed of the transverse waves so produced in the string is _______ m s–1 .

Q24.Two objects A and B are placed at 15 cm and 25 cm from the pole in front of a concave mirror having radius of curvature 40 cm . The distance between images formed by the mirror is: (1) 40 cm (2) 60 cm (3) 160 cm (4) 100 cm

Q24.An ice cube has a bubble inside. When viewed from one side the apparent distance of the bubble is 12 cm . When viewed from the opposite side, the apparent distance of the bubble is observed as 4 cm . If the side of the ice cube is 24 cm , the refractive index of the ice cube is (1) 3 (2) 2 2 3 (3) 6 (4) 4 5 3

Q24.The energy density associated with electric field E and magnetic field B of an electromagnetic wave in free space is given by ( ε0− permittivity of free space, μ0− permeability of free space) (1) UE = 2ε0E2 , UB = 2μ0 B2 (2) UE = ε0E22 , UB = 2μ0B2 μ0B2 , UB = 2 (3) UE = ε0E22 , UB = μ0B22 (4) UE = 2ε0E2

Q24.A thin rod having a length of 1 m and area of cross-section 3 × 10-6 m2 is suspended vertically from one end. The rod is cooled from 210°C to 160°C. After cooling, a mass 𝑀 is attached at the lower end of the rod such that the length of rod again becomes 1 m. Young's modulus and coefficient of linear expansion of the rod are 2 × 1011 N m-2 and 2 × 10-5 K-1, respectively. The value of 𝑀 is ______ kg. (Take 𝑔= 10 m s-2 )

Q24.A capacitor of capacitance 900 µ F is charged by a 100 V battery. The capacitor is disconnected from the battery and connected to another uncharged identical capacitor such that one plate of uncharged capacitor connected to positive plate and another plate of uncharged capacitor connected to negative plate of the charged capacitor. The loss of energy in this process is measured as 𝑥× 10-2 J. The value of 𝑥 is ______.

Q24.A series LCR circuit is connected to an AC source of 220 V , 50 Hz. The circuit contains a resistance R = 80 Ω, an inductor of inductive reactance XL = 70 Ω, and a capacitor of capacitive reactance XC = 130 Ω . The power factor of circuit is x . The value of x is: 10

Q24.In an experiment with sonometer when a mass of 180 g is attached to the string, it vibrates with fundamental frequency of 30 Hz. When a mass 𝑚 is attached, the string vibrates with fundamental frequency of 50 Hz. The value of 𝑚 is ______ g.

Q24.A microscope is focused on an object at the bottom of a bucket. If liquid with refractive index 5 is poured 3 inside the bucket, then microscope have to be raised by 30 cm to focus the object again. The height of the liquid in the bucket is : (1) 75 cm (2) 50 cm (3) 18 cm (4) 12 cm

Q24.A plane electromagnetic wave of frequency 20 MHz propagates in free space along x-direction. At a particular → → space and time E = 6. 6ˆj V m−1 . What is B at this point? (1) 2. 2 × 10−8ˆkT (2) −2. 2 × 10−8ˆiT (3) −2. 2 × 10−8ˆkT (4) 2. 2 × 10−8ˆi T

Q24.A hole is drilled in a metal sheet. At 27 °C, the diameter of hole is 5 cm. When the sheet is heated to 177 °C, the change in the diameter of hole is 𝑑× 10-3 cm . The value of 𝑑 will be _____, if coefficient of linear expansion of the metal is 1 . 6 × 10-5 / ∘C

Q24.The length of a wire becomes 𝑙1 and 𝑙2 when 100 N and 120 N tension are applied respectively. If 1 10𝑙2 = 11𝑙1, then the natural length of wire will be 𝑥𝑙1. Here the value of 𝑥 is 𝜋