Tag: physics

Questions Related to physics

If the mass of the sheet at the top of the aneroid barometer used as an altimeter is increased, what will be the effect on the reading?

various types of barometer fluids physics

  1. It will reduce.

  2. It will increase.

  3. No effect.

  4. Can't be determined

Show answer
Correct Option: B
Explanation:

If the top sheet in an aneroid barometer is heavier, it will displace lesser. So, it gives reading corresponding to a lower pressure with a lighter thin sheet. Lower pressure is observed at more heights and hence, the reading of the altimeter will increase.

Water vaporizes under vacuum conditions. Mark the statement which is correct with respect to using water as a barometric fluid.

various types of barometer fluids physics
  1. It will show the true atmospheric pressure.
  2. It will be clearly seen in the glass tube.
  3. It will not show true atmospheric pressure.

  4. None

Show answer
Correct Option: C
Explanation:

WATER VAPORISES UNDER VACUUM CONDITIONS.THUS WATER BAROMETER WILL NOT SHOW TRUE ATMOSPHERIC PRESSURE.

Atmospheric pressure at a certain place is equivalent to $78cm$ of mercury. That place is

various types of barometer fluids physics

  1. $250m$ above sea level

  2. $250m$ below sea level

  3. $125m$ above sea level

  4. at the sea level

Show answer
Correct Option: B
Explanation:

Atmospheric pressure at that place is $78cm$ of mercury.
We know that the atmospheric pressure at the sea level is $76cm$ of mercury.
This means, this place has an atmospheric pressure $(78-76)cm=2cm$ more than the atmospheric pressure at the sea level.
We know that the atmospheric pressure increases by $1cm$ for every $125m$ decrease in height.
So, this place is $(125 \times 2)m=250m$ below sea level.

Gradual fall in the mercury level in a barometer indicates
various types of barometer fluids physics

  1. possibility of rain

  2. possibility of thunderstorm

  3. fair weather

  4. dry and sunny weather

Show answer
Correct Option: A
Explanation:

Gradual fall in the mercury level occurs at low pressure- If there is too much moisture in the air, indicates the possibility of rain

Which is the most accurate instrument to measure pressure and is used as a standard?

various types of barometer fluids physics

  1. Aneroid Barometer

  2. Mercury Barometer

  3. Barograph

  4. Manometer

Show answer
Correct Option: B
Explanation:

Answer is B

In the mercury barometer, atmospheric pressure balances a column of mercury, the height of which can be precisely measured. To increase their accuracy, mercury barometers are often corrected for ambient temperature and the local value of gravity.

In the interference pattern, energy is

luminous intensity measurements physics

  1. created at the position of maxima

  2. destroyed at the positions of minima

  3. conserved but is redistributed

  4. not conserved

Show answer
Correct Option: C
Explanation:

conserved but is redistributed

A lamp placed 60 cm from a screen produces the same illumination as a standard 100 W lamp placed 90 cm away on the other side of the screen. The luminous intensity of the first lamp is 

luminous intensity measurements physics

  1. $49.44W$

  2. $44.44W$

  3. $54.44W$

  4. $34.44W$

Show answer
Correct Option: B
Explanation:

For same illumination $\dfrac{Power} { r^{2}}$ will be same


=> $\dfrac {100} { 0.9^{2}} = \dfrac {P} {0.6^{2}}$
=> P = $44.44 W$

Light has a wave nature, because-

luminous intensity measurements physics

  1. the light travel in a straight line

  2. Light exhibits phenomenon of reflection and refraction

  3. Light exhibits phenomenon interference

  4. Light exhibits phenomenon of photo electric effect.

Show answer
Correct Option: C

Light with energy flux 36$\mathrm { w } / \mathrm { cm } ^ { 2 }$ is incident on a well polished metal slate of side 2$\mathrm { cm }$ . Theforce experienced by it is

luminous intensity measurements physics

  1. 0.96$\mu N$

  2. 0.24$\mu N$

  3. 0.12$\mu N$

  4. 0.36$\mu N$

Show answer
Correct Option: A

If relative luminosity is $0.65$ then the luminous flux of a $10 W$ source is

luminous intensity measurements physics

  1. $12130.6$

  2. $4125.5$

  3. $4352.5$

  4. $4452.5$

Show answer
Correct Option: D
Explanation:

Luminous flux of a 10W source=Relative luminosity$\times$ luminous flux of 555nm source of 10W

=$0.65\times (685\times 10)=4452.5$