1.The total power radiated by the sun is about 3.83 x1026 Watts. How many kilograms of protons and electrons are transformed into helium every second? Note: For a fusion reaction the fraction of mass converted to energy is about 0.007.
2.The mass of the Sun is about 1.99 x1030 kilograms. If we assume this is all hydrogen and about one tenth (0.1) is in the core, how long will the sun burn? Enter your answer in years (use yr as the unit for years). Hint: Calculate the number of seconds the Sun will last and then divide by the number of seconds in a year to get years. For comparison, the Earth is about 4.5 x109 yr old.
3.The diffraction of radiation can be used to determine the spacing between atoms. In practice, the wavelength of the radiation used should be restricted to a value which is of the same order of magnitude as the interatomic distances to be determined. Such experiments are commonly performed using X-rays (electromagnetic radiation), however a beam of subatomic particles, such as of neutrons or electrons, may also be used if their corresponding de Broglie wavelength is of the appropriate magnitude.
a.Calculate the de Broglie wavelength of a neutron (mn = 1.67493×10-27 kg) moving at one seven thousandth of the speed of light (c/7000).
(Enter at least 4 significant figures.)
b.Calculate the velocity of an electron (me = 9.10939×10-31 kg) having a de Broglie wavelength of 159.6 pm.
4. The amount of 14C in an old, isolated sample of vegetation is 0.653 that expected from a present day sample with an equivalent carbon content. Calculate the age of the old sample in years.