On a summer afternoon, the sand on the beach can get very hot. when you step on the sand in bare feet, you can burn yourself.
which of the following sentences best describes how this happens?
heat from the sun is transferred to the sand without direct contact. this heat is then transferred to your feet without direct contact.
heat from the sun is transferred to the sand without direct contact. this heat is then transferred to your feet by direct contact.
heat from the sun is transferred to the sand by direct contact. this heat is then transferred to your feet by direct contact.
heat from the sun is transferred to the sand by direct contact. this heat is then transferred to your feet without direct contact.

Some material consisting of a collection of microscopic objects is kept at a high temperature. a photon detector capable of detecting photon energies from infrared through ultraviolet observes photons emitted with energies of 0.3 ev, 0.5 ev, 0.8 ev, 2.0ev, 2.5ev, and 2.8ev. these are the only photon energies observed. (a) draw and label a possible energy-level diagram for one of the microscopic objects, which has four bound states. on the diagram, indicate the transitions corresponding to the emitted photons. explain briefly. (b) would a spring–mass model be a good model for these microscopic objects? why or why not? (c) the material is now cooled down to a very low temperature, and the photon detector stops detecting photon emissions. next, a beam of light with a continuous range of energies from infrared through ultraviolet shines on the material, and the photon detector observes the beam of light after it passes through the material. what photon energies in this beam of light are observed to be significantly reduced in intensity (“dark absorption lines”)? explain briefly.

Which is the correct symbol for an isotope of iodine with 53 protons and 78 neutrons?

Arowboat passenger uses an oar to push the boat off the dock by exerting a force of 40n for 3.0s. what impulse acts on the boat.