Physics · Waves · NEET
No. They measure different directions. Amplitude is measured up and down from the rest line (how far a particle moves), while wavelength is measured along the wave (how long one full wave is). On a graph amplitude is a vertical height and wavelength is a horizontal distance. In the equation y = a sin(kx - wt), the letter a is the amplitude and lambda is hidden inside k.
They describe the same thing but in opposite ways. Frequency (f) counts how many complete waves pass a point in one second, measured in hertz (Hz). Time period (T) is the time taken for just one complete wave to pass, measured in seconds. They are linked by T = 1/f. So a high frequency wave has a short time period.
No. Amplitude and frequency are independent. You can make a wave taller (bigger amplitude) without changing how often it repeats (frequency). Amplitude is set by how hard you disturb the medium and it decides the energy and loudness. Frequency is set by the source only. For NEET, remember: changing amplitude never changes frequency, wavelength or wave speed.
No, this is a common trap. Frequency is how many waves pass per second. Wave speed is how fast the wave pattern moves through the medium. They are connected by v = f x lambda. The medium fixes the speed, and the source fixes the frequency. So if you change the medium the speed and wavelength change, but the frequency stays the same.
Amplitude is a displacement, so its unit is metre (m). Wavelength is a distance, also metre (m). Frequency is number per second, so its unit is hertz (Hz), which is the same as per second (1/s). Time period is a time, so its unit is second (s).
Try the real previous-year questions from this chapter — each with the answer and a full solution.
T = 1/f, or equally f = 1/T. Time period and frequency are reciprocals of each other. For example, a wave of frequency 50 Hz has a time period T = 1/50 = 0.02 s.
NCERT defines wavelength as the minimum distance between two points that have the same phase. In simple terms, it is the distance between two consecutive crests or two consecutive troughs, denoted by lambda and measured in metres.
Here a is the amplitude directly. The angular wave number k = 2 pi / lambda carries the wavelength, and the angular frequency w = 2 pi f = 2 pi / T carries the frequency and period. So from a given equation you can read amplitude directly and get lambda, f and T from k and w.
Amplitude. A bigger amplitude means the wave carries more energy, so a sound wave is louder and a light wave is brighter. Frequency instead decides pitch of sound or colour of light, not loudness or brightness.
The source keeps producing waves at the same rate, so frequency cannot change. But the medium sets the wave speed. Since v = f x lambda and f is fixed, a change in v forces lambda to change. This is a favourite NEET reasoning point.
