I know this may be a stupid question but I need to find an example of a crystal solid besides quartz.I also need an example of a amorphous solid if you have any suggestions....Thanks
Technically, they aren't more efficient (an object whose sole purpose is to turn work into heat can't help but to be 100% efficient), but they are more effective. They put more of the energy into radiant energy that will warm up objects in the beam. So less goes into heating the air (which can be easily lost to convection).
I agree with BB's answer (B); efficiency, measured by total heat output, would be the same for both heaters. However, it's possible for a quartz heater to be less effective if any of its radiant power is directed toward a window where it could escape. My own experience is that radiant heat from a 1 or 2 kw heater isn't worth much unless you're pretty near it; a blown standard heater seems more useful in warming up a room. Heating the walls with radiant energy increases the heat loss rate compared to warmer air and colder walls.
