In a photoelectric-effect experiment it is observed that no current flows unless the wavelength is less than 570nm .
A)What is the work function of this material?
W0= in eV
B) What is the stopping voltage required if light of wavelength 420nm is used?
stopping voltage in V
To find the work function of the material in the photoelectric effect experiment, we can use the equation:
Kinetic energy of electrons (K.E.) = Energy of incident photons - Work function
A) To calculate the work function (W0) in eV, we need to convert the given wavelength of 570 nm to energy using the equation:
Energy of incident photons = (hc) / λ
where h is Planck's constant (6.626 x 10^-34 J.s), c is the speed of light (3 x 10^8 m/s), and λ is the wavelength.
First, let's convert the given wavelength from nanometers (nm) to meters (m):
λ = 570 nm = 570 x 10^-9 m
Now, substitute the values into the equation to find the energy of incident photons:
Energy of incident photons = (6.626 x 10^-34 J.s * 3 x 10^8 m/s) / (570 x 10^-9 m)
Next, we need to convert the energy from joules to electron volts (eV). One electron volt is equal to 1.602 x 10^-19 J.
So, divide the energy by 1.602 x 10^-19 J/eV to get the work function in electron volts (eV):
W0 = (Energy of incident photons) / (1.602 x 10^-19 J/eV)
B) To find the stopping voltage required when using light of wavelength 420 nm, we can use the equation:
Stopping voltage = (hc / e) * (1 / λ - 1 / λ0)
where e is the charge of an electron (1.602 x 10^-19 C), hc is the product of Planck's constant and the speed of light, λ is the wavelength of the incident light, and λ0 is the threshold wavelength (570 nm).
First, convert the given wavelength from nanometers (nm) to meters (m):
λ = 420 nm = 420 x 10^-9 m
Substitute the values into the equation to calculate the stopping voltage:
Stopping voltage = ((6.626 x 10^-34 J.s * 3 x 10^8 m/s) / (1.602 x 10^-19 C)) * (1 / 420 x 10^-9 m - 1 / 570 x 10^-9 m)
Now you have the result for both the work function (W0) in eV and the stopping voltage in volts.