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.
Children get allergies from coming into contact with allergens. Allergens can be inhaled, eaten, or injected (from stings or medicine) or they can come into contact with the skin. 1  Pollens from trees, grasses, and weeds.  Molds, both indoor and outdoor.