Answer:
2.9 E14 Hz
Explanation:
As we know by Einstein's equation that energy incident on the photo sensitive surface will be used by the surface to eject electron out of the surface with some kinetic energy.
This is given by

now the threshold frequency is the minimum frequency of the incident photons due to which electrons are ejected out with minimum kinetic energy or least kinetic energy.
So here when KE = 0 in the graph then corresponding to that position the frequency will be given as threshold frequency
so here from graph when KE = 0

Complete Question
The complete question is shown on the
Answer:
The ascending order would be 2nd < 1st < 3rd
Explanation:
Generally the the Normal force is mathematically represented as

=> 
For the first drawing the value
is between that of the the second and the third drawing so the Normal force would also be between the normal forces of the second and the third drawing
For the second drawing whose value of
is less than that of the first and the third the normal force would also be less than that of the first and third
For the the third drawing whose value is (90°) which is higher than the first and the second the normal force would also be higher than the first and the second
Answer:
the impedance of the circuit is 25.7 ohms.
Explanation:
It is given that,
Voltage, V = 50 volts
Frequency, f = 60 Hz
Resistance, R = 25 ohms
Capacitive resistance, 
Inductive resistance, 
We need to find the impedance of the circuit. It is given by :


Z = 25.7 ohms
So, the impedance of the circuit is 25.7 ohms. Hence, this is the required solution.
I believe the answer is stored energy.