Three ways to emit electronsइलेक्ट्रॉन उत्सर्जन के तीन तरीकेThree ways to emit electrons

NCERT Sec 11.2 · Class 12 Physics · Chapter 11 · interactive diagram

Parts and what they mean

• Thermionic emission (heat) (तापायनिक उत्सर्जन (ऊष्मा)) — Heating the metal gives free electrons enough thermal energy to come out (e.g. hot filament).
• Field emission (strong field) (क्षेत्र उत्सर्जन (प्रबल क्षेत्र)) — A very strong electric field (of the order of 10⁸ V m⁻¹) pulls electrons out of the metal, as in a spark plug.
• Electric field E (विद्युत क्षेत्र E) — Points from the + plate towards the metal (−); electrons feel a force opposite to E, so they are pulled out of the metal.
• Photoelectric emission (light) (प्रकाश-विद्युत उत्सर्जन (प्रकाश)) — Light of suitable (high enough) frequency falling on the metal ejects electrons — photoelectrons.
• Incident light (आपतित प्रकाश) — Its frequency must be above the threshold frequency of the metal.
• Emitted electron (उत्सर्जित इलेक्ट्रॉन) — Negatively charged; same e/m as cathode-ray particles, whichever way it was emitted.

Original diagram drawn by Simple Learning Hub, based on NCERT Sec 11.2. Report a mistake