NEET PHYSICS-QUESTION ANSWER & SOLUTION (7)

QUESTION-1

The wave nature of  electrons was experimentally verified by

 [A]   Hertz                                         [B]    Einstein

 [C]   Davisson and Germer             [D]   de Broglie

ANSWER :

                                                                                  ANSWER:[C]

SOLUTION:

From de Broglie hypothesis,the wavelength associated with an electron beam accelerated through 54 V should be 1.66 X 10^-10 m.

The tentatively estimated wavelength is near that assessed from de Broglie theory 1.65 X 10^-10 m. This demonstrates the presence of de Broglie waves.

QUESTION-2

QUESTION-3

Fundamental frequencies of two identical strings  of same material A and B are 450 Hz and 300 Hz respectively,then  the ratio of tension in the string A and B will be

ANSWER:

ANSWER – [B]

SOLUTION:

EXPRESSION FOR THE FUNDAMENTAL FREQUENCY OF THE STRING:

RATIO OF TENSIONS IN THE STRING:

QUESTION:4

A coil of radius R rotating about a diametric axis with angular velovity ω in a uniform magnetic field B.Find the value of maximum voltage developed. Radius R=10 cm and  B=5×10^-5 T.For half rotation it takes a time of 0.2 sec.

[A] 3×10^-5 V                                            

[B] 2.5×10^-5 V                                            

[C] 5×10^-6 V   

[D] 5×10^-5 V                                                                                      

ANSWER :

ANSWER:[B]

SOLUTION:

Magnetic flux linked with the coil

INDUCED EMF: