Question

1. your friends say that they saw a special nail polish that changes color when it is out in the sun. can light from the sun cause the nail polish to change color?

• 1 point

○ no. light is not a physical thing, so it cannot change physical things like nail polish.
○ yes. light from the sun can pull energy out of the nail polish, causing it to change color
○ yes. the nail polish can take in energy from the light, causing it to change color
○ no. light can only change things by warming them up, so it cannot cause the nail polish to change color

1. dentists use a soft, clay - like material to make a filling for a cavity. the filling stays soft under the light of the dentist’s lamp, but it hardens when the dentist shines an ultraviolet flashlight on it. why does light from the ultraviolet flashlight harden the filling when light from the lamp does not?

• 1 point

○ because ultraviolet light carries energy, and light from the lamp does not.
○ because the filling material can take in energy from ultraviolet light, but not from the light from the lamp
○ because ultraviolet light pulls energy out of the filling material, and light from the lamp does not.
○ because ultraviolet light carries hardening molecules, but light from the lamp does not.

Explanation:

• For question 5: Light is a form of energy. When the nail - polish absorbs energy from sunlight (light is a physical entity in terms of energy transfer), it can undergo a color change. The first option is wrong as light is a form of energy (a physical concept in terms of energy transfer). The second option is wrong because light does not "pull" energy out of the nail - polish; rather, the nail - polish absorbs energy. The fourth option is wrong as light can cause changes other than just warming (like chemical changes due to energy absorption).
• For question 6: All light (including from the lamp and ultraviolet light) carries energy. The key is that the filling material can absorb energy from ultraviolet light (which has a higher energy per photon in some cases relevant to its chemical composition) but not from the light of the lamp (the lamp light may not have the right energy for the material to undergo the hardening chemical reaction). The first option is wrong as lamp light also carries energy. The third option is wrong as it's about absorption (taking in) of energy, not pulling out. The fourth option is wrong as light does not carry "hardening molecules".

Answer:

1. Yes. The nail polish can take in energy from the light, causing it to change color
2. Because the filling material can take in energy from ultraviolet light, but not from the light from the lamp