Pumping your legs at the right speed to make a swing move is a demonstration of Refraction Resonance Interference Diffraction Doppler Effect

## Step 1<br />The problem is asking us to identify the physical phenomenon that is demonstrated when you pump your legs at the right speed to make a swing move. The options provided are Refraction, Resonance, Interference, Diffraction, and Doppler Effect.<br /><br />## Step 2<br />Let's analyze each option:<br /><br />### Refraction<br />Refraction is the change in direction of a wave due to a change in its speed. This is most commonly observed when a wave passes from one medium to another. This doesn't apply to the situation of a swing moving.<br /><br />### Resonance<br />Resonance occurs when an object is made to vibrate at its natural frequency by the application of a periodic force having that frequency. In the case of a swing, when you pump your legs at the right speed, you are causing the swing to vibrate at its natural frequency, which is the definition of resonance.<br /><br />### Interference<br />Interference is the interaction of waves that results in the combination of two or more electromagnetic or sound waves in such a way that the total effect is a new wave pattern. This doesn't apply to the situation of a swing moving.<br /><br />### Diffraction<br />Diffraction is the spreading of waves as they pass through an aperture or around an obstacle. This doesn't apply to the situation of a swing moving.<br /><br />### Doppler Effect<br />The Doppler Effect is the change in frequency or wavelength of a wave in relation to an observer who is moving relative to the wave source. This doesn't apply to the situation of a swing moving.<br /><br />## Step 3<br />Based on the above analysis, the correct answer is Resonance.