Which statements describe elements? Check all that apply -atoms of the same element can have different numbers of protons. A.-Atoms of the same element always have the same number of electrons. B.– Atoms of the same element can have different numbers of neutrons. C.– Atoms of the same element always have the same number of neutrons. D.– Atoms of the same element always have the same number of protons. E.– Atoms of the same element can be isotopes of that element.

The free body diagram shows a box being pulled to the left up a 25-degree incline. the magnitude of the normal force is

Antireflective coatings on solar cells are often made by applying a thin film of silicon nitride (sinx), which has an index of refractive of 1.2, on the top of the silicon solar cell, which has a refractive index of about 3.5. however, the sun emits radiation of various wavelengths which the solar cell absorbs, and the antireflective coating can only absolutely minimize the reflection of one of these wavelengths. the coating thickness is chosen to reduce the reflection of green/yellow light (e = 2.2 ev), which is the most intense color in the solar spectrum (shown below). which of the following coatings would minimize reflection of green/yellow light? the answer is 820 nm how? what is the angular width of the central maximum of an electron traveling at 2 x 108 m/s going through a single slit of width 1 mm.

Suppose that f : rn → rm and that a ∈ k, where k is a connected subset of rn . suppose further that for each x ∈ k there exists a δx > 0 such that f(x) = f(y) for all y ∈ bδx (x). prove that f is constant on k; that is, f(x) = f(a) for all x ∈ k