A vibration record is not a picture of a wave traveling across a room — Physics & Environmental Science

A source graph shows position in millimeters against time in seconds. Its vertical midpoint is an equilibrium position, amplitude is a departure from that midpoint, and period is the interval between equivalent cycles. The graph cannot directly give a spatial wavelength because its horizontal axis is time. A separate spatial snapshot or wave speed is needed to connect the two descriptions.

Sound uses material compression and expansion; electromagnetic waves can travel through vacuum. Pitch, intensity and loudness are different quantities, and a decibel difference describes a logarithmic intensity ratio under a stated reference. Moving sound sources change front spacing relative to the medium, while vacuum-light Doppler shifts use a different relativistic model.

Optics also needs disciplined geometry. Measure reflection/refraction angles from the normal, not from the surface. For lenses, draw actual rays from one object point and distinguish their real intersection from backward extensions. A thin-lens equation and ray diagram should agree on image side, size and orientation. The assumptions matter as much as the arithmetic.