Wave Optics — Physics STD 12 Science — Question

Which of the following statements is incorrect?

If the potential difference applied across X-ray tube is V volts, then approximately minimum wavelength of the emitted X-rays will be

(a)

(b)

(c)

(d)

In given figure, the potentiometer wire AB has a resistance of 5 W and length 10 m. The balancing length AM for the emf of 0.4 V is

(a) 0.4 m

(b) 4 m

(c) 0.8 m

(d) 8 m

Assertion  :   A loosely round helix made of stiff wire is suspended vertically with the lower end just touching a dish of mercury. When a current is passed through the wire, the helical wire executes oscillatory motion with the lower end jumping out of and inside of mercury.

Reason     : When electric current is passed through helix, a magnetic field is produced both inside and outside the helix.

(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 the assertion and reason both are false.

The focal length of a concave mirror is 10 cm. On placing an object at 10 cm in front of the mirror, its image will be formed:

Suppose, the electron in a hydrogen atom makes transition from n = 3 to n = 2 in 10^-8s. The order of the torque acting on the electron in this period, using the relation between torque and angular momentum as discussed in the chapter on rotational mechanics is:

When the convergent nature of a convex lens will be less as compared with air

(a) In water

(b) In oil

(c) In both (a) and (b)

(d) None of these

To convert a 800 mV range milli voltmeter of resistance 40 W into a galvanometer of 100 mA range, the resistance to be connected as shunt is

(a) 10 W

(b) 20 W

(c) 30 W

(d) 40 W

Order of  q/m  ratio of proton, α -particle and electron is

(a) e > p > α

(b) p > α > e

(c) e > α > p

(d) None of these

Which of the following represents the binding energy of a nucleus: