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 answer these questions, we need to understand the photoelectric effect and the equations involved. Let's start with some background information:

The photoelectric effect refers to the emission of electrons from a metal surface when light (photons) is incident on it. In this experiment, no current flows unless the wavelength of the incident light is less than 570nm. This observation implies that electrons are only ejected when the energy of the incident photons is greater than a certain threshold value, which depends on the material. This threshold energy is called the work function (W₀) of the material.

A) Now, the work function (W₀) can be calculated using the following equation:
W₀ = hν - φ
where h is the Planck's constant (6.626 x 10⁻³⁴ J·s), ν is the frequency of light, and φ is the work function in joules.

To convert the work function from joules to electron volts (eV), we can use the fact that 1 eV = 1.602 x 10⁻¹⁹ J.

To find the work function (W₀) in eV, we need the frequency (ν) of the light. We know the wavelength (λ) of the light being used is 570nm. The frequency (ν) can be calculated using the equation: ν = c/λ, where c is the speed of light (3 x 10⁸ m/s).

1. Convert the wavelength from nm to meters: λ = 570nm = 570 x 10⁻⁹ m
2. Calculate the frequency (ν): ν = c/λ = (3 x 10⁸ m/s) / (570 x 10⁻⁹ m)
3. Use the obtained frequency (ν) in the equation: W₀ = hν - φ, and rearrange the equation to solve for the work function (φ) in joules.
4. Finally, convert the work function from joules to eV: W₀ (in eV) = φ (in eV) / (1.602 x 10⁻¹⁹ J/eV)

B) To find the stopping voltage, we can use the equation:
eV₀ = hν - W₀
where e is the elementary charge (1.602 x 10⁻¹⁹ C) and V₀ is the stopping voltage.

To find the stopping voltage (V₀) when the light of wavelength 420nm is used, we need to calculate the frequency (ν) and then use the equation above.

1. Convert the wavelength from nm to meters: λ = 420nm = 420 x 10⁻⁹ m
2. Calculate the frequency (ν): ν = c/λ = (3 x 10⁸ m/s) / (420 x 10⁻⁹ m)
3. Use the obtained frequency (ν) and the work function (W₀) in the equation: eV₀ = hν - W₀, and rearrange the equation to solve for the stopping voltage (V₀).

By following these steps, we can find the values for both the work function (W₀) and the stopping voltage (V₀).