To calculate the minimum number of photons of light of wavelength 4000 Angstrom which provide energy 1 J, we will use the following formula:

Energy of a Photon = (Planck's Constant * Speed of Light) / Wavelength



We know that 1 eV is equal to 1.6 x 10^-19 J. Therefore, we can convert 1 J to eV as follows:

1 J = (1 / 1.6 x 10^-19) eV
= 6.25 x 10^18 eV



We can use the formula mentioned above to calculate the energy of a photon of wavelength 4000 Angstrom:

Energy of a Photon = (Planck's Constant * Speed of Light) / Wavelength
= (6.626 x 10^-34 Js * 3 x 10^8 m/s) / (4000 x 10^-10 m)
= 4.97 x 10^-19 J



Now, we can calculate the minimum number of photons required to provide 1 J of energy as follows:

Number of Photons = Energy Required / Energy of a Photon
= 6.25 x 10^18 eV / (4.97 x 10^-19 J / 1 eV)
= 1.26 x 10^20 photons

Therefore, the minimum number of photons of light of wavelength 4000 Angstrom which provide energy 1 J is 1.26 x 10^20 photons.