Electric Charges and Fields — Physics STD 12 Science — Question

A direct X-ray photograph of the intestines is not generally taken by the radiologists because

(a) Intestines would burst on exposure to X-rays

(b) The X-rays would not pass through the intestines

(c) The X-rays will pass through the intestines without causing a good shadow for any useful diagnosis

(d) A very small exposure of X-rays causes cancer in the intestines

If a proton and electron have same de Broglie wavelength, then:

Lenz's law gives:

When a charged particles moves in a uniform magnetic field in a direction perpendicular to the field, then the path of the particle will be:

Photoelectric effect supports quantum nature of light because:

Which of the transitions in hydrogen atom emits a photon of lowest frequency  (n = quantum number)

(a) n = 2 to n = 1

(b) n = 4 to n = 3

(c) n = 3 to n = 1

(d) n = 4 to n = 2

The two rails of a railways track, insulated from each other and the ground, are connected to a milli voltmeter. What is the reading of the milli voltmeter when a train travels at a speed of 20 ms^-1 along the track, given that the vertical component of the earth's magnetic field is 0.2 × 10^-4 Wbm^-2 and the rails are separated by 1m?

Assertion  :   An electric bulb is first connected to a dc source and then to a ac source having the same brightness in both the cases.

Reason    : The peak  value of voltage for an A.C. source is  times the root mean square voltage.

(a) If both assertion and reason are true and the reason is the correct explanation of the assertion.

(b) If both assertion and reason are true but reason is not the correct explanation of the assertion.

(c) If assertion is true but reason is false.

(d) If assertion is false but reason is true.

Consider the following two statements A and B and identify the correct choice in the given answer

A :  The characteristic X-ray spectrum depends on the nature of the material of the target.

B :  The short wavelength limit of continuous X-ray spectrum varies inversely with the potential difference applied to the X-rays tube

(a) A is true and B is false	(b) A is false and B is true
(c) Both A  and B  are true	(d) Both A and B are false

A long solenoid has n turns per meter and current I A is flowing through it. The magnetic field at the ends of the solenoid is

(a)

(b)

(c) Zero

(d) 2