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.
This type of allergy refers to a pollen allergy, such as trees, weeds and grasses. Perennial allergies, on the other hand, are usually present year-round, and include allergens such as pet dander and house dust mite. Molds can be a seasonal or perennial allergy trigger. Seasonal allergies are also often referred to as hay fever. Learn all you've ever wanted to know (and more) about hay fever.