JEE Questions (Set 1)

#1. Energy of an electron in an excited hydrogen atom is -3.4 eV. Its angular momentum will be

(d) 4.20 × 10^–34 Js

(c) 1.51 × 10^–34 Js

(a) 3.72 × 10^–34 Js

(b) 2.10 × 10^–34 Js

#2. Which of the following electromagnetic waves has minimum frequency?

(d) Radio Waves

(a) Microwaves

(c) Ultrasonic wave

(b) Audible waves

#3. The mutual inductance of a pair of coils, each of N turns, is M henry. If a current of I ampere in one of the coils is brought to zero in t second, the emf induced per turn in the other coil, in volt, will be

(b) MI/t

(c) MN/It

(a) NMI/t

(d) MI/Nt

#4. Electrons in a certain energy level n = n1, can emit 3 spectral lines. When they are in another energy level, n = n2. They can emit 6 spectral lines. The orbital speed of the electrons in the two orbits are in the ratio of

(d) 4:3

(a) 3:4

(c) 1:2

(b) 2:1

#5. A coil of inductance 300 mH and resistance 2Ω is connected to a source of voltage 2V. The current reaches half of its steady state value in

(c) 0.3 s

(d) 0.15 s

(b) 0.05 s

(a) 0.1 s

#6. The power radiated from antenna of length l is proportional to

(c) (l/λ)^3

(b) (l/λ)^2

(a) (l/λ)

(d) √l/λ

#7. A beam of electrons is moving with constant velocity in a region having simultaneous perpendicular electric and magnetic fields of strength 20 Vm^–1 and 0.5 T respectively at right angles to the direction of motion of the electrons. Then the velocity of electrons must be

(d) 1/40 m/s

(c) 40 m/s

(b) 20 m/s

(a) 8 m/s

#8. A radiation of energy ‘E’ falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (c = Velocity of light)

(c) E/c^2

(a) 2E/c

(b) 2E/c^2

(d) E/c

#9. A coil has resistance 30 ohm and inductive reactance 20 ohm at 50 Hz frequency. If an ac source, of 200 volt, 100 Hz, is connected across the coil, the current in the coil will be

(a) 4.0 A

(b) 8.0 A

(c) 20/√13 A

(d) 2.0 A

#10. A and B have different dimensions. Then which of the following relation will be meaningful?

(d) [e^A/B]

(b) [A-B]

(a) [A/B]

(c) [A+B]

#11. . In Rutherford scattering experiment, the number of α-particles scattered at 60° is 5 × 10^6. The number of α-particles scattered at 120° will be

(d) None of these

(a) 15 × 10^6

(c) ⅗ × 10^6

(b) 5/9 × 10^6

#12. A sinusoidal voltage of amplitude 25 volt and frequency 50Hz is applied to a half wave rectifier using P-n junction diode. No filter is used and the load resistance is 1000Ω. The forward resistance Rf of an ideal diode is 10Ω. The percentage efficiency of rectifier is

(b) 30%

(d) 40%

(a) 20%

(c) 15%

#13. A neutron traveling with a velocity v and kinetic energy E has a perfectly elastic head-on collision with a nucleus of an atom of mass number A at rest. The fraction of total energy retained by the neutron is approximately

(a) [(A – 1)/(A + 1)]^2

(d) [(A + 1)/A]^2

(c) [(A – 1)/A]^2

(b) [(A + 1)/(A – 1)]^2

#14. A pure semiconductor has equal electron and hole concentration of 10^16 m^–3. Doping by indium increases number of hole concentration nh to 5 ×10^22 m^–3. Then, the value of number of electron concentration ne in the doped semiconductor is

(d) 2 × 10^6/m^3

(c) 2 × 10^9/m^3

(a) 10^6/m^3

(b) 10^22/m^3

#15. A person can see clearly only up to a distance of 30 cm. He wants to read a book placed at a distance of 50 cm from his eyes. What is the power of the lens of his spectacles?

(d) -2.0 D

(c) -1.67 D

(a) -1.0 D

(b) -1.33 D

#16. . If E1, E2, E3 are the respective kinetic energies of an electron, an alpha-particle and a proton, each having the same de-Broglie wavelength, then

(b) E2 > E3 > E1

(a) E1 > E3 > E2

(c) E1 > E2 > E3

(d) E1 = E2 = E3

#17. The cathode of a photoelectric cell is changed such that the work function changes from W1 to W2 (W2 > W1). If the current before and after changes are I1 and I2, all other conditions remaining unchanged, then (assuming hν > W2)

(d) I1 < I2 < 2 I1

(b) I1 > I2

(c) I1 = I2

(a) I1 < I2

#18. In a photoelectric experiment, with light of wavelength λ, the fastest electron has speed v. If the exciting wavelength is changed to 5λ/4, the speed of the fastest emitted electron will become

(a) v√5/4

(c) Less than v√5/3

(d) Greater than v√5/3

(b) v√5/3

#19. A radio transmitter transmits at 830 kHz. At a certain distance from the transmitter magnetic field has amplitude 4.82 × 10^–11 T. The electric field and the wavelength are respectively:

(b) 0.14 N/C, 36m

(a) 0.014 N/C, 36m

(c) 0.14 N/C, 360m

(d) 0.014 N/C, 360m

#20. A nucleus disintegrates into two nuclear parts which have their velocities in the ratio 2 : 1. Ratio of their nuclear sizes will be

(d) 1 : 2^⅓

(b) 1 : 3^½

(c) 3^½ : 1

(a) 2^⅓ : 1

#21. The condition for obtaining secondary maxima in the diffraction pattern due to single slit is

(c) a sinΘ = (2n - 1) λ

(d) a sinΘ = nλ/2

(a) a sinΘ = nλ

(b) a sinΘ = (2n - 1) λ/2

#22. Television signals on earth cannot be received at distances greater than 100 km from the transmission station. The reason behind this is that

(a) the receiver antenna is unable to detect the signal at a distance greater than 100 km

(b) the TV programme consists of both audio and video signals

(c) the TV signals are less powerful than radio signals

(d) the surface of earth is curved like a sphere

#23. An electric dipole is placed in a uniform electric field. The dipole will experience

(b) a force that will displace it in a direction opposite to the field.

(c) a torque which will rotate it without displacement

(a) a force that will displace it in the direction of the field

(d) a torque which will rotate it and a force that will displace it

#24. A plane electromagnetic wave is incident on a material surface. If the wave delivers momentum p and energy E, then

(d) p = 0, E ≠ 0

(b) p ≠ 0, E = 0

(a) p = 0, E = 0

(c) p ≠ 0, E ≠ 0

#25. . If a simple pendulum of length l has maximum angular displacement θ, then the maximum K.E. of bob of mass m is

(b) mg/2l

(d) Mgl (1-cosΘ)

(c) Mgl sin Θ/2

(a) ½ ml/g

Results