Examples of reflection. Plane wave, plane surface. The phase of the reflected sound waves from hard surfaces and the reflection of string waves from their ends determines whether the interference of the reflected and incident waves will be constructive or destructive.
The tendency to develop allergies is often hereditary, which means it can be passed down through genes from parents to their kids. But just because you, your partner, or one of your children might have allergies doesn't mean that all of your kids will definitely get them, too.
Some have suggested that environmental factors or early exposure to certain foods can cause allergies later in life, while others say that allergies are caused by genetics. To test the latter theory, many researchers study identical twins to see if sets of twins share allergies.