Summary of results:

Maria Mitchell's score on this quiz was 40% (any incorrect choices are highlighted in red).

#1. Can one find optical radiation and gamma-rays which travel at the same speed?

#2. Why can't humans see infrared waves?

#3. If the mass of a proton is 1.6726 × 10 kg and the mass of an electron is 9.1094 × 10 kg, how many electrons does it take to match the mass of a single proton?

#4. Which of the following must be present in an atom?

#5. How many neutrons are there in a deuterium atom (²H₁)?

Elapsed Time: 10.58 minutes

#1. Can one find optical radiation and gamma-rays which travel at the same speed?

Yes

No

Gamma-rays are extremely high-energy photons, with wavelengths of roughly 0.1 Angstroms, while optical radiation has wavelengths around 5,000 Angstroms. Gamma-rays are thus shorter wavelength, higher frequency, and shorter period forms of energy than optical radiation.

However, all such light travels at the same speed, the speed of light, 300,000 kilometers per second. The rate of speed is independent of the amount of energy that a photon carries, so gamma-rays, x-rays, ultraviolet and optical photons, infrared radiation, and radio waves all travel at the same speed.

      

#2. Why can't humans see infrared waves?

They lie at wavelengths too long for us to perceive them.

They vary so slowly that they are easy to overlook.

They are usually masked by radio signals.

They tend to propagate through the Earth's interior, rather than on the surface.

All electromagnetic waves travel at the same speed (in a vacuum). What distinguishes one from another is its wavelength (or frequency). Humans can see light which falls between 3800 and 7400 Angstroms (violet to red in color), while infrared waves have wavelengths of order one to 1,000 microns (10,000 to 10 million Angstroms). They are thus invisible to our eyes.

However, we can build cameras and telescopes which can detect them!

      

#3. If the mass of a proton is 1.6726 × 10 kg and the mass of an electron is 9.1094 × 10 kg, how many electrons does it take to match the mass of a single proton?

Write your answer in the box, using a standard format for numbers. For example, if the answer is ten type "10" of "1.e1", and if the answer is twenty, type "20" or "2.e1".

The mass of a proton might seem tiny at first, but when compared to that of an electron we realize that there are far lighter particles in the Universe.

      

#4. Which of the following must be present in an atom?

electron	proton
neutron	photon

Each atom is defined as a member of a particular element, by the numbers of protons that it contains (from one to roughly one-hundred).

A standard, neutral atom of hydrogen contains just one proton and one electron. If it loses the electron, it becomes a positively charged ion of hydrogen. An electron, or a neutron, on its own is no atom, and neither is a photon.

      

#5. How many neutrons are there in a deuterium atom (²H₁)?

Write your answer in the box, using a standard format for numbers. For example, if the answer is one, type "1", and if the answer is two, type "2".

When identifying which isotope of an element is under discussion, we precede the element shorthand name (H for hydrogen) with a superscript of the total number of protons and neutrons (1 + 1 = 2) and follow it with a subscript of the number of protons (1).