The relationship between the frequency (f) of an electromagnetic wave, the speed of the wave (which is the speed of light, c) and its wavelength

is given by

Since the wavelength of the radiation in the problem is

, by substituting numbers in the formula we can get the frequency:
I would think force. Because friction has to have force to work ^-^
Heat lost or gained, H = mc(θ₂ - θ₁)
Where m = mass, c = Specific heat capacity, θ₂= final temperature, θ₁ = initial temperature
m = 200g, c = 0.444 J/g°C, θ₁ = 22 °C (Since it was cooled).
H = 6.9 kj = 6.9 *1000J = 6900 J
6900 = 200*0.444* (θ₂ - 22)
6900/(200*0.444) = θ₂ - 22
77.70 = θ₂ - 22
θ₂ - 22 = 77.7
θ₂ = 77.7 + 22 = 99.7
So initial temperature before cooling ≈ 100°C . Option C.
Answer:
The direction of the magnetic field at point Z; Into the screen
Explanation: