Physics | NEET Entrance Exam | Under Graduate Entrance Exams Online Objective Test

Under Graduate Entrance Exams NEET Entrance Exam # Physics Wave Optics Prepare / Learn

Q1. According to Huygens construction relation between old and new wave fronts is

A. new wave front is parallel to old wave front

B. new wave front is perpendicular to old wave front

C. new wave front is the forward envelope of the secondary waves

D. new wave front is tangential to old wave front

Answer : Option C
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Magnetism and Matter Prepare / Learn

Q2. Compass needle of known magnetic moment m in a uniform magnetic field field experiences a torque equal to

A. τ⃗ =m⃗ .B⃗

\vec{τ} = 2 π \vec{m} \times \vec{B}

\vec{τ} = μ_{0} \vec{m} \times \vec{B}

C. τ⃗ =μ0m⃗ ×B⃗

D. τ⃗ = m⃗ ×B⃗

Answer : Option D
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Gravitation Prepare / Learn

Q3. A ‘central’ force is always directed

A. at a fixed angle to the position vector of the point of application of the force with respect to the fixed point

B. along the position vector of the point of application of the force with respect to the fixed point

C. at a varying angle to the position vector of the point of application of the force with respect to the fixed point

D. perpendicular to the position vector of the point of application of the force with respect to the fixed point

Answer : Option B
Explaination / Solution:

The motion of a particle under a central force F always remains in the plane defined by its initial position and velocity.This may be seen by symmetry. Since the position r, velocity v and force F all lie in the same plane, there is never an acceleration perpendicular to that plane, because that would break the symmetry between "above" the plane and "below" the plane.

To demonstrate this mathematically, it suffices to show that the angular momentum of the particle is constant. This angular momentum L is defined by the equation

L = r \times p = r \times m v

Under Graduate Entrance Exams NEET Entrance Exam # Physics Electronic Devices Prepare / Learn

Q4. Motion of hole is a convenient way of describing

A. the actual motion of bound electrons

B. the actual motion of free electrons

C. the actual motion of energy gap

D. the actual motion of conduction electrons

Answer : Option A
Explaination / Solution:

The holes are just the abscence of a electron in a energy band. But its easier to describe the abscence of a electron as a single moving positive charge than it is to describe the motion of all the other electrons in the band. In a band you have N electrons. Remove one of those electrons(by for instance p-doping) and you have N-1 electrons left. Now you can either choose to describe this with the behavior of those N-1 electrons. Or you can choose to describe it as if there is one single hole moving around in the band. So mathematicly the holes behave just like a positivly charged electron.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Motion in A Straight Line Prepare / Learn

Q5. For one dimensional motion displacement is the

Δ x = (x_{2} + x_{1}) / 2

Δ x = (x_{2} + x_{1}) / 2

∆ x = 2 (x_{2} + x_{1})

B.

Δx=2(x2+x1)

change in position:

Δx=x2−x1

D. change in position:

Δ x = x_{2} + x_{1}

Answer : Option C
Explaination / Solution:

Displacement is defined to be the change in position of an object. It can be defined mathematically with the following equation:

$D i s p l a c e m e n t = ∆ x = x_{2} - x_{1}$

$x_{2}$ refers to the value of the final position.

$x_{1}$ $x_{1}$ refers to the value of the initial position.

$∆ x$ is the symbol used to represent displacement.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Electromagnetic Waves Prepare / Learn

Q6. Angular frequency ω and wave vector k are related by

A. k =

\frac{π}{λ}

B. k =

\frac{π}{2 λ}

C. k =

\frac{4 π}{λ}

D. k =

\frac{π}{λ}

Answer : Option D
Explaination / Solution:
No Explaination.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Waves Prepare / Learn

Q7. in longitudinal waves, the constituents of the medium

A. oscillate at 30

^{\circ}

to the direction of wave propagation

B. oscillate at 40

^{\circ}

to the direction of wave propagation

C. oscillate perpendicular to the direction of wave propagation

D. oscillate along the direction of wave propagation

Answer : Option D
Explaination / Solution:

In longitudinal wave motion, medium particles oscillates or vibrates in same direction of wave propagation to produce compression & rarefaction in wave propagation.

Under Graduate Entrance Exams NEET Entrance Exam # Physics Electromagnetic Induction Prepare / Learn

Q8. According to Farady's law for a coil having N turns, the total induced emf is given by

A. e=μ0NdϕBdt

B. e=μ0N2dϕBdt

C. e=−dϕBdte=−NdϕBdt

D. e=−dϕBdt

Answer : Option C
Explaination / Solution:

The induced electromotive force in any closed circuit is equal to the negative of the time rate of change of the magnetic flux enclosed by the circuit.

induced emf for a coil having 1 turns will be $e = - \frac{d ϕ_{B}}{d t}$

The flux of all the turns will be added up. So the induced emf for a coil having N turns will be $e = - N \frac{d ϕ_{B}}{d t}$

Under Graduate Entrance Exams NEET Entrance Exam # Physics Dual Nature of Radiation and Matter Prepare / Learn

Q9. Stopping potential in the experimental set up shown in figure is

A. negative potential

V_{0}

given to the plate A for which the photocurrent stops or becomes zero

B. positive potential

V_{0}

given to the plate A for which the photocurrent stops increasing

C. positive potential

V_{0}

given to the plate A for which the photocurrent saturates

D. positive potential

V_{0}

given to the plate A for which the photocurrent stops or becomes zero

Answer : Option A
Explaination / Solution:

The negative potential of the plate at which the photo electric current becomes zero is called stopping potential or cut-off potential. Its value is negative because some electron reach to the plate with their kinetic energy at zero potential.

Under Graduate Entrance Exams NEET Entrance Exam # Physics System of Particles and Rotational Motion Prepare / Learn

Q10. considering binary (double) stars in our frame of reference, the trajectories of the stars are a combination of

A. (i) uniform motion in a circle of the centre of mass and (ii) circular orbits of the stars about the centre of mass

B. (i) uniform motion in a straight line of the centre of mass and (ii) circular orbits of the stars about the centre of mass

C. i) uniform motion in a straight line of the centre of mass and (ii) elliptical orbits of the stars about the centre of mass

D. i) uniform motion in a straight line of the centre of mass and (ii) straight line motion of the stars about the centre of mass

Answer : Option B
Explaination / Solution:

A double star or visual double is a pair of stars that appear close to each other in the sky as seen from Earth when viewed through an optical telescope.

In absence of external force Centre of mass of double star moves like a free particle. In Centre of mass frame both stars moving in a circle about the Centre of mass which is at rest and both star are diametrically opposite to each other.

Thus in our frame of reference, the trajectories of the stars are a combination of (i) uniform motion in a straight line of the Centre of mass and (ii) circular orbits of the stars about the Centre of mass.

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