Why does ultraviolet light cause calcite to glow, while light from a desk lamp does not?

• A. Ultraviolet light is absorbed by calcite, while visible light is reflected, preventing fluorescence.
• B. Calcite only reacts to light with longer wavelengths, such as ultraviolet, and not to shorter wavelengths like visible light.
• C. The desk lamp emits infrared light, which is not energetic enough to cause calcite to glow.
• D. Ultraviolet light has a higher frequency and energy than visible light, allowing it to excite electrons in calcite to higher energy states, resulting in fluorescence.

Answer: (D)

Verified step by step guidance

1. Understand that fluorescence occurs when a substance absorbs light energy and then emits light at a different wavelength.
2. Recognize that ultraviolet (UV) light has a higher frequency and therefore higher energy compared to visible light emitted by a desk lamp.
3. Know that in calcite, electrons can be excited to higher energy states only if the incoming light has enough energy, which UV light provides but visible or infrared light does not.
4. When UV light excites the electrons in calcite, these electrons return to their original energy levels by releasing energy in the form of visible light, causing the glow (fluorescence).
5. Visible light from a desk lamp lacks sufficient energy to excite the electrons in calcite, so it is mostly reflected rather than absorbed and re-emitted as fluorescence.