Physics
Wavefunctions, tunneling and wave packets.
a cloud of probability that spreads, scatters and interferes
A Gaussian wave packet in 2D drifts, spreads and splits at a potential bump; brightness shows |ψ|² and colour shows the quantum phase.
walls force whole half-waves, so energy comes in steps
A particle trapped between hard walls can only hold standing waves, so its energy is quantized as n² and superpositions slosh at beat frequencies.
a wave leaks through a wall it can't climb
A quantum packet hitting a barrier higher than its energy still partly gets through: transmission falls off exponentially with barrier width.