When ultraviolet light is incident on certain metallic p articles are emitted. These particles are called

Analyze the question The question describes the photoelectric effect: light of high enough frequency (such as ultraviolet) shines on a metal surface, and particles are emitted from the metal. We need the name of these emitted particles.

Explain the concept In the photoelectric effect:

• Light travels as packets of energy called photons, with energy E = hf.
• If the photon energy is at least the metal's work function (Φ), it can free an electron from the metal surface.
• The electrons that are emitted are called photoelectrons.

Einstein's photoelectric equation is:

hf = Φ + ½mv²ₘₐₓ

where:

• hf is the energy of the incident photon
• Φ is the work function (the minimum energy needed to free an electron)
• ½mv²ₘₐₓ is the maximum kinetic energy of the emitted electron

Go through the options

• A. Positrons: These are positively charged anti-electrons. They are not emitted in the photoelectric effect.
• B. Protons: These are heavy particles in the nucleus and are not released from a metal surface by light.
• C. Photoelectrons: These are electrons ejected from a metal by incident light. ✔
• D. Photons: These are the light particles that are incident on the metal. They are not emitted from it.

Answer The particles emitted are photoelectrons, which is option C.

Exam tip Remember: photons go in, photoelectrons come out. The "photo" part means light caused the emission, and "electron" tells you what is emitted.