Move your hand around in front of the mirror until you can feel the hot spot. This spot will be close to a point in space called the mirror’s focal point. Look into the mirror and find the visible image of the heater: This image of the heater will also be near the focal point.
Now look into the mirror and move around, observing your reflection. Move toward and away from the mirror, and see how your image and the images of the objects around you change.
Next, move the heater off the axis of the mirror or closer to the mirror. Search around, using the back of one hand as an infrared-radiation detector. Find where the infrared radiation from the heater is concentrated. This will be the position of the infrared "image" of the heater. Locate the visible-light image of the heater with your eyes. Notice that the infrared energy from the heater comes back together at the visible-light image position. Notice also that when the heater is off-axis, the image point is not the focal point.
Place your face close to the mirror and talk into the mirror. Keep talking as you move away from the mirror. At one point, your voice will sound much louder. At this point, the sound waves radiating from your mouth bounce off the mirror and are concentrated at your ear. When this happens, the mirror is making a sound image of your voice at the position of your ear.