Question

melanin, found in the epidermis, is a chromophore that gives our skin its color. uva waves activate melanin already present in our skin, causing our skin to tan quickly. uvb waves cause skin cells to produce more melanin, slowly tanning our skin over a few days. our epidermis also contains the chromophore 7 - dehydrocholesterol (7 - dhc). 7 - dhc can be converted into vitamin d3 when it absorbs certain wavelengths of uvb waves. vitamin d3 is an essential nutrient for healthy bones and muscles. the amount of vitamin d3 our skin produces depends in part on how long we stay in the sun, the time of day, the season, and the weather. most people in the united states do not spend enough time in the sun to produce all the vitamin d3 they need. however, foods like salmon and egg yolks can provide additional vitamin d3. complete the sentences. skin cells in the epidermis produce melanin when waves interact with the outer layer of our skin. this increase in melanin causes the skin to darken.

Explanation:

The text states "UVB waves cause skin cells to produce more melanin, slowly tanning our skin over a few days." So, the first blank should be filled with "UVB" as it's the wave type that causes melanin production in skin cells (epidermis - the outer layer). The second blank is about the effect of increased melanin which is stated as "tanning" (making the skin darker).

Answer:

Skin cells in the epidermis produce melanin when UVB waves interact with the outer layer of our skin. This increase in melanin causes the skin to tan/darken.