Sodium has a work function of 2.46 eV. (a) Find the cutoff wavelength and cutoff frequency for the photoelectric effect.
(b) What is the stopping potential if the incident light has a wavelength of 181 nm?

Explanation:

given, work function of Φ = 2.46 eV.

converting the eV to joule, we have

2.45 * 1.6*10^-19 J

The cutoff wavelength is the wavelength where the incoming light does not have enough energy to free an electron, i.e. all of

the photon’s energy will be channeled into trying overcoming the work function barrier.

It is mathematically given as

Φ = hf

f = Φ/h

f = (2.46 * 1.6*10^-19) / 6.63*10^-34

f = 3.936*10^-19 / 6.63*10^-34

f = 5.94*10^14 Hz as our cut off frequency

λf = c,

λ = c/f

λ = 3*10^8 / 5.94*10^14

λ = 5.05*10^-7

λ = 505 nm as our cut off wavelength

K(max) = hf - Φ

K(max) = hc/λ - Φ

K(max) = [(6.63*10^-34 * 3*10^8) / 181*10^-9] - 3.936*10^-19

K(max) = (1.989*10^-25/181*10^-9) - 3.936*10^-19

K(max) = 1.1*10^-18 - 3.936*10^-19

K(max) = 7.064*10^-19 J or 4.415 eV

V(s) = K(max) / e

V(s) = 4.612 V

force is based upon mass and acceleration.the statement is not always true.

it can be explained from newton's second law of motion.

as per newton's second law of motion the rate of change of momentum is directly proportional to the applied force and takes place along the direction of force.

mathematically it can be written as -

                                              ⇒      

here   k is the proportionality constant whose value is 1.

                                                            [a is the acceleration=dv/dt]

hence we see that force not only depends on mass and acceleration but also on velocity and rate of change of mass. force f will depend on mass and acceleration only when mass is constant.

hence the statement that force is based upon mass and acceleration is false.