Which argument best explains the charge of an atomic nucleus?
an atomic nucleus is positively charged because it is composed of neutrons.
an atomic nucleus is positively charged because it is composed of protons.
an atomic nucleus is negatively charged because it is composed of electrons.
an atomic nucleus is negatively charged because it is composed of neutrons.

The correct statement is an atomic nucleus is positively charged because it is composed of protons.

Explanation:

Atomic nucleus is present in the center of an atom and consists of 2 sub-atomic particles which are protons and neutrons.

Protons are the sub-atomic particles which carry positive charge and neutrons are the sub-atomic particles which carry no charge.

Electrons are another sub-atomic particles which carry negative charge but do not exist inside the nucleus. They revolve around the nucleus.

The charge on the atomic nucleus is positive due to the presence of protons.

Hence, the correct statement is an atomic nucleus is positively charged because it is composed of protons.

you'd use the equation that establishes a relationship between  energy  and  wavelength, which looks like this

e=h⋅cλ, where

λ  - the wavelength of the photon; c  - the speed of light, usually given as  3⋅108m/s; h  -  planck's constant, equal to  6.626⋅10−34j s

plug the value you were given for the energy of the photon in the above equation to get the wavelength

e=h⋅cλ⇒λ=h⋅ce

λ=6.626⋅10−34js⋅3⋅108ms−1.257⋅10−24j=1.581⋅10−1m