12th Standard Physics English Medium Free Online Test Volume 2 One Mark questions 2020

12th Standard

Reg.No. :
•
•
•
•
•
•

Physics

Time : 00:25:00 Hrs
Total Marks : 25
25 x 1 = 25
1. When a biconvex lens of glass having refractive index 1.47 is dipped in a liquid, it acts as a plane sheet of glass. This implies that the liquid must have refractive index,

(a)

less than one

(b)

less than that of glass

(c)

greater than that of glass

(d)

equal to that of glass

2. When light is incident on a soap film of thickness 5×10–5 cm, the wavelength of light reflected maximum in the visible region is 5320 Å. Refractive index of the film will be,

(a)

1.22

(b)

1.33

(c)

1.51

(d)

1.83

3. Two plane mirrors are at 45° to each other. If an object is placed between them than the number of images will be

(a)

5

(b)

9

(c)

7

(d)

8

4. A ray of light is incidenting normally on a .plane mirror. The angle of reflection will be

(a)

(b)

90°

(c)

will not be reflected

(d)

None of these

5. A point object 0 is placed between two plane mirrors as shown is figure The distance by mirror M2 from it are

(a)

2 mm, 8 mrn, 18 mm

(b)

2 mm, 18 mm, 28 mm

(c)

2 mm, 18 mm, 22 mm

(d)

2 mm, 18 mrn, 58 mm

6. All of the following statement are correct except

(a)

The magnification produced by a convex mirror is always less than one

(b)

A virtual, erect same sized image can be obtained using a plane mirror

(c)

A virtual, erect magnified iinage can be formed using a concave mirror

(d)

A real, inverted, same-sized image can be formed using a convex mirror

7. When a metallic surface is illuminated with radiation of wavelength λ, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2λ, the stopping potential is $\frac{V}{4}$. The threshold wavelength for the metallic surface is

(a)

(b)

(c)

$\frac{5}{2}λ$

(d)

8. A light source of wavelength 520 nm emits 1.04 × 1015 photons per second while the second source of 460 nm produces 1.38 × 1015 photons per second. Then the ratio of power of second source to that of first source is

(a)

1.00

(b)

1.02

(c)

1.5

(d)

0.98

9. As the intensity of incident light increases

(a)

K.E of emitted photo electrons increases

(b)

photoelectric current decreases

(c)

photoelectric current increases

(d)

K.E of emitted photo electrons decreases

10. According to special theory of relativity the only constant in all frames is

(a)

mass

(b)

length

(c)

time

(d)

velocity of light

11. The light photon has _______ nature.

(a)

wave

(b)

particle

(c)

matter

(d)

dual

12. Total angular momentum of a moving electron is an integral multiple of _______

(a)

h

(b)

λ

(c)

$\frac { h }{ 2\pi }$

(d)

13. The ratio of the wavelengths for the transition from n=2 to n=1 in Li++, He+ and H is

(a)

1:2:3

(b)

1:4:9

(c)

3:2:1

(d)

4:9:36

14. Wave number is defined as the number of wave

(a)

produced in one second

(b)

in a distance of 1 metre

(c)

in a distance of 3 x 108 m

(d)

in a distance of λ metre

15. Arrange the spectral lines Hα, Hβ, Hγ, Hδ in the increasing order of their wavelength

(a)

Hα, Hβ, H, Hδ

(b)

Hδ, H, Hβ, Hα

(c)

Hβ, Hα Hδ, H

(d)

Hα, Hβ, Hγ, Hδ

(a)

first

(b)

second

(c)

third

(d)

fourth

17. A forward biased diode is treated as

(a)

An open switch with infi nite resistance

(b)

A closed switch with a voltage drop of 0V

(c)

A closed switch in series with a battery voltage of 0.7V

(d)

A closed switch in series with a small resistance and a battery

18. To obtain sustained oscillation in an oscillator,

(a)

Feedback should be positive

(b)

Feedback factor must be unity

(c)

Phase shift must be 0 or 2π

(d)

All the above

19. The output current versus time curve of a rectifier is shown in figure. The average value of the output current is

(a)

0

(b)

$\frac{I_0}{2}$

(c)

$\frac { 2{ I }_{ 0 } }{ \pi }$

(d)

Io

20. To obtain OR gate from NOR gate, you will need __________

(a)

one NOR gate

(b)

one NOT gate

(c)

two NOT gate

(d)

one OR gate

21. Energy gap between valence band and conduction band is called as the _____________

(a)

forbidden energy gap

(b)

conduction band gap

(c)

valence band gap

(d)

filled band gap

22. The internationally accepted frequency deviation for the purpose of FM broadcasts

(a)

75 kHz

(b)

68 kHz

(c)

80 kHz

(d)

70 kHz

23. The made of propagation used by short wave broadcast services is

(a)

space wave

(b)

skywave

(c)

ground wave

(d)

both (a) & (c)

24. The materials used in Robotics are

(a)

Aluminium and silver

(b)

Silver and gold

(c)

Copper and gold

(d)

Steel and aluminum

25. Muscle wires can contract by _________ when electric current is passed through them

(a)

5%

(b)

7%

(c)

25%

(d)

50%