All electrons ejected from a surface by incident light of wavelength 200 nm can be stopped before traveling 1 m in a uniform electric field of 4 N/C. The work function of the surface is:

1.5 mW of 400 nm light is directed at a photoelectric cell. If 0.1% of the incident photons produce photoelectrons, the current in the cell is:

Stopping potentials of 24, 100, 110, 115 kV are measured for photoelectrons emitted from a certain element when irradiated with monochromatic X-rays. The element is used as a target in an X-ray tube. The energy of the K line is:

The frequency of incident light falling on a photosensitive plate is doubled, then the maximum kinetic energy of the emitted photoelectrons will become:

The work function of a substance is 4 eV. The approximate longest wavelength of light that can cause photo-emission is:

A modern 200-watt sodium street lamp emits yellow light of wavelength 0.6 µm. Assuming it is 25% efficient in converting electrical energy to light, the number of photons emitted per second is:

The human eye can barely detect yellow light (6000 Å) that delivers 1.7 × 10⁻¹⁸ watt to the retina. Nearly how many photons per second does the retina receive?