H2 Physics Flashcards

What is the photoelectric effect?

Answer: Emission of electrons from a metal surface when light of sufficient frequency is incident on it

The photoelectric effect is the emission of electrons from a metal surface when light above the threshold frequency is incident on it — evidence for the particle nature of light (photons).

What is the de Broglie wavelength of a particle?

Answer: λ = h/mv

The de Broglie wavelength: λ = h/p = h/mv, where h is Planck's constant, m is mass, and v is velocity. This shows matter has wave-like properties.

In a transformer, the primary coil has 200 turns and the secondary has 50 turns. If the input is 240V, what is the output?

Answer: 60V

Vs/Vp = Ns/Np → Vs = 240 × (50/200) = 240 × 0.25 = 60V. This is a step-down transformer.

What does the area under a velocity-time graph represent?

Answer: Displacement

The area under a velocity-time graph represents the displacement of the object. Area above the time axis is positive displacement; area below is negative.

What is the equation for the energy of a photon?

Answer: E = hf

The energy of a photon is E = hf, where h is Planck's constant (6.63 × 10⁻³⁴ J s) and f is the frequency of the electromagnetic radiation.

What happens to the resistance of a semiconductor as temperature increases?

Answer: Resistance decreases

In semiconductors, increasing temperature provides energy to free more charge carriers (electrons and holes), increasing conductivity and decreasing resistance — opposite to metals.