The work function of cesium surface is 2.0eV
(a)find the maximum kinetic energy of the ejected electrons when the surface is illuminated by violet light with wavelenght = 4.13 x 10^3 Angstroom unit
h = 6.63 x 10^9-34)Js
(b) what is the threshold wavelenght ( the largest wavelenght) for the photoelectric effect to occur with this metal?
maximumKE= photonenergy - work function
Threshold energy= work function
Threshold freq= thresholdenergy/planck's
wavelength*frequency= speedlight
calculate wavelength.
To find the maximum kinetic energy of the ejected electrons when the surface is illuminated by violet light, you can use the equation:
maximumKE = photon energy - work function
where the photon energy is given by:
photon energy = (Planck's constant * speed of light) / wavelength
(a)
Given:
Work function = 2.0 eV = 2.0 x 1.6 x 10^-19 J (since 1 eV = 1.6 x 10^-19 J)
Wavelength = 4.13 x 10^3 Angstrom = 4.13 x 10^-7 m
Planck's constant (h) = 6.63 x 10^-34 J s
First, let's calculate the photon energy:
photon energy = (6.63 x 10^-34 J s * 3 x 10^8 m/s) / (4.13 x 10^-7 m)
photon energy ≈ 1.229 x 10^-19 J
Now, we can calculate the maximum kinetic energy:
maximumKE = 1.229 x 10^-19 J - 2.0 x 1.6 x 10^-19 J
maximumKE ≈ -2.971 x 10^-19 J
Note: The resulting value for the maximum kinetic energy is negative, which indicates that the electrons are not ejected. This implies that the violet light with the given wavelength does not have enough energy to overcome the work function and eject electrons.
(b)
To calculate the threshold wavelength (the largest wavelength) for the photoelectric effect to occur with this metal, we can calculate the threshold energy:
threshold energy = work function = 2.0 x 1.6 x 10^-19 J
Now, we can use the equation: wavelength * frequency = speed of light
First, calculate the threshold frequency:
threshold frequency = threshold energy / Planck's constant
threshold frequency = (2.0 x 1.6 x 10^-19 J) / (6.63 x 10^-34 J s)
threshold frequency ≈ 4.82 x 10^14 Hz
Next, calculate the speed of light:
speed of light = wavelength * frequency
speed of light = threshold wavelength * threshold frequency
To find the threshold wavelength, rearrange the equation:
threshold wavelength = speed of light / threshold frequency
threshold wavelength ≈ (3 x 10^8 m/s) / (4.82 x 10^14 Hz)
Calculating the threshold wavelength:
threshold wavelength ≈ 6.22 x 10^-7 m
Therefore, the threshold wavelength (largest wavelength) for the photoelectric effect to occur with this metal is approximately 6.22 x 10^-7 m (or 622 nm).