Physics - Online Test
Q1. Shape of the wave front of light emerging out of a convex lens when a point source is placed at its focus.
Answer : Option D
Explaination / Solution:
The rays of light becomes parallel after passing through a convex lens if the object is placed at focus. The shape of wavefront is plane as wavefront is perpendicular to rays.
Q2. A wire of given length is first bent in one loop and the next time it is bent in three loops. If the same current is passed in both the cases, the ratio of the magnetic field induction at their centres will be
Answer : Option C
Explaination / Solution:
If the wire has length L, when it is coiled into a coil of 1 turn of radius r, When it is coiled into a coil of 3 turns of radius r’ .The magnetic field in the first case and in the second case,
Q3. To produce N – type crystal Ge or Si may be doped with a substance that is
Answer : Option B
Explaination / Solution:
If a pentavalent element from the Vth Group such as Antimony (Sb) is added to pure geranium (Ge) or silicone (Si), then four electrons of (Sb) will form covalent bonds with four (Ge) or (Si) atoms. The fifth electron of 'Sb' is free to move which makes (Ge) or (Si) a good conductor. This type of material is called n-type substance.
Q4. A truck accelerates at 1 m / from rest. What is its velocity in m/s at a time of 2 sec?
Answer : Option D
Explaination / Solution:
Initial velocity u = 0 m/s
final velocity = v
Time t = 2 s
Acceleration a = 1 m/s2
We know,
v = u + at
=> v = 2 m/s
Q5. The frequency of the third harmonic of a closed organ pipe is equal to which of the overtones?
Answer : Option B
Explaination / Solution:
No Explaination.
Q6. A straight wire carries a current of 50 A and the loop as in figure is moved to the right with a constant velocity, . Take a and assume that the loop has a large resistance. Induced emf in the loop at the instant when x = 0.2 m is
Answer : Option A
Explaination / Solution:
Q7. State the part of the electromagnetic spectrum to which 1057 MHz (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift)..Belongs
Answer : Option B
Explaination / Solution:
No Explaination.
Q8. Wavelength associated with a photon having energy 3.1eV is
Answer : Option A
Explaination / Solution:
λ(inA∘)=12375E(ineV)λ=123753.1≃4000A∘
Q9. baseband signal refers to the
Answer : Option A
Explaination / Solution:
No Explaination.
Q10. A motorcycle stunt rider rides off the edge of a cliff. Just at the edge his velocity is horizontal, with magnitude 9.0 m/s. Find the magnitude of the motorcycle’s position vector after 0.50s it leaves the edge of the cliff.
Answer : Option B
Explaination / Solution:
The motorcycle’s x- and y-coordinates at t=0.50 s are
x = vox t= =4.5 m
y= = -1.2m
The negative value of y shows that the motorcycle is below its starting point.
The motorcycle’s distance from the origin at t=0.50 s is r= =4.7 m
