A tank 20 m deep and 7m wide is layered with 8m of oil,6m of water and 5m of mercury.complete total hydroatatic force.(density o
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Answer:
a) the longest wavelength of the light that will eject electrons from the silicon surface is 258.7891 nm
b) maximum kinetic energy will electrons reach the anode is 0.5098 eV
Explanation:
Given:
Wavelength range = 141-295 nm
Potential of 3.5 V
For the silicon, the work function is Φ = 4.8 eV = 7.68x10⁻¹⁹J
Questions:
a) What is the longest wavelength of the light that will eject electrons from the silicon surface, λ = ?
b) With what maximum kinetic energy will electrons reach the anode,
a) The longest wavelength that will eject electrons:
Here
h = Planck's constant = 6.625x10⁻³⁴J s
c = speed of light = 3x10⁸m/s
Substituting values:
b) The maximum kinetic energy (one electron):
Now, you need to calculate the potential difference:
Here
e = charge of electron = 1.6x10⁻¹⁹C
Substituting:
Now, the maximum kinetic energy of the electrons:
Kmax = 4.0098 - 3.5 = 0.5098 eV
Work is done when a force is in the same direction as the object moves.
Explanation:
The work done by a force in moving an object is given by the equation
where
F is the magnitude of the force
d is the displacement of the object
is the angle between the directions of F and d
From the equation, we notice the following:
- Work is done by a force when the force is in the same direction as the object moves. In fact, in this case,
, and so
, which means that the work done simply becomes
- When the force is perpendicular to the motion of the object,
and
, which means that no work done
- Technically, work is also done when the force is not parallel to the motion of the object: in this case, the factor
means that only the component of the force parallel to the direction of motion contributes to do work on the object.
Therefore, the correct answer is
Work is done when a force is in the same direction as the object moves.
Learn more about work:
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