Question of the day

Q- Two identical thin, parallel and coherent beams of same intensity and wavelength λ are incident on a screen lies in the same plane at angles θ1 and θ2  with the normal. Find the fringe width on the screen.  

Q- A small ideal mirror of mass 10 mg is suspended by a light thread of length 10 cm. Find the angle through which the thread will be deflected when a short laser pulse of energy 15 J is shot on the mirror horizontally and normally to the surface of the mirror and reflected completely.

Solution:

Q- A galvanometer together with an unknown resistance is connected with two identical batteries of each 1.5 V. When the batteries are connected in series, the galvanometer records a current 1.0 A and when the batteries are in parallel, the current is 0.6 A. What is the internal resistance of the bat...

Q- Two blocks of mass m and M are attached to the two ends of a light spring of constant k. The system is held by m such that M is suspended through the spring in air. Now the system is lowered slowly such that M just touches the tabletop and m is released. Find the maximum displacement of m before ...

Q- An Airplane with a wing span of 50 m is flying in earth's total magnetic field of 5.4×10^-5  Wb m^-2 and the angle of dip is 30°. Calculate the emf induced across the tips of the wings.

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Q- A particle is projected in a vertical plane from a point O with velocity u at angle α to the horizontal. Find the time at which the particle is moving at angle θ  to the horizontal.

Solution:

Q- A box of base area as a square of side 0.50 m, height of 1 m and mass 200 kg rests on horizontal floor of a truck with one edge of the base is perpendicular to direction of motion of the truck. If the acceleration of the truck is gradually increased, what is the minimum value of friction coeffici...

Q- The vibrations of a string of length 60 cm fixed at both ends are represented by the equation 

                y  = 4 sin (π x/15) cos (96 π t)  

(here x and y are in cm and t in seconds) 

(a)  What is the maximum displa...

Q- A compound microscope is used to enlarge an object kept at a distance 0.03m from it’s objective which consists of four thin convex lenses in contact and has focal length 0.02m. If a lens of focal length 0.1m is removed from the objective, then by what distance the eye-piece of the microscope must...

Q- A bead slides down along a frictionless stiff wire of length L which is bent in form of a serpentine coil of length L/2 and placed vertically as in figure. What is the slide time to reach the ground? The gap between the turns is much less than the length of the wire.

Solution: