The energy required by the excitation of the line is:
ΔE = hν = hc / λ
where:
ΔE = energy difference
h = Planck constant
ν = line frequency
c = speed of light
λ = line wavelength
The energy difference must be supplied by the electron, supposing it transfers all its kinetic energy to excite the line:
Therefore,
And solving for v we get:
Plugging in numbers (after trasforing into the correct SI units of measurement):
=9.4 · 10⁵ m/s
Hence, the electron must have a speed of
9.4 · 10<span>
⁵ m/s in order to excite the <span>492nm</span> line.</span>
It is an example of reactivity
iron usually rusts due to oxygen in the air
Answer:
e = 30 V
Explanation:
given,
N = 30 turns
Area = 0.25 m²
angular speed = ω = 100 rad/s
Magnetic field = 0.04 T
maximum induced emf in the loop = ?
e = N B A ω
e = 30 x 0.04 x 0.25 x 100
e = 30 V
hence, the maximum emf induced in the loop is equal to e = 30 V
Answer:
D.
Explanation:
Given that your boat departs from the bank of a river that has a swift current parallel to its banks. If you want to cross this river in the shortest amount of time, you should direct your boat: so that it drifts with the current.
If the boat moves perpendicular to the current, the current flow will be the resistance to the movement of the boat. So, it's better for the boat to drifts perpendicularly with the current.
The best answer is therefore option D.
Answer: 317.0 m/s
Explanation:
The motion of the bullet is a projectile motion, with:
- a uniform motion with constant speed v along the horizontal direction
- an accelerated motion with constant acceleration toward the ground
We know that the starting height of the bullet is h=1.4 m. If we consider the vertical motion only, the initial velocity is zero, so we can write:
The bullet reach the ground when y(t)=0, so the time taken is
During this time, the bullet travels d=168 m horizontally, so its horizontal speed (which is equal to the initial speed of the bullet) is given by