In 1913, henry moseley systematically studied the x-ray spectra of various elements. he made use of bragg's discovery of x-ray diffraction to calculate the wavelengths of the spikes seen in the spectrum of x-rays emitted when high-energy electrons impact a target. he then found an empircal law relating the frequency f of the most intense x-ray spike--known as the k_{\alpha} line--to the atomic number z of the element. that empirical law, known as moseley's law, is

f=(2.48\times10^{15}\; {\rm hz})(z-1)^2.

Clothing made of several thin layers of fabric with trapped air in between, often called ski clothing, is commonly used in cold climates because it is light, fashionable, and a very effective thermal insulator. so it is no surprise that such clothing has largely replaced thickand heavy old-fashioned coats. (a) consider a jacket made of five layers of 0.1-mm-thick synthetic fabric (k = 0.13 w/m·°c) with 1.5-mm-thick air space (k = 0.026 w/m·°c) between the layers. assuming the inner surface temperature of the jacket to be 28°c and the surface area to be 1.25 m2, determine the rate of heat loss through the jacket when the temperature of the outdoors is 0°c and the heat transfer coefficient at the outer surface is 25 w/m2·°c. (b) what would your response be if the jacket is made of a single layer of 0.5-mm-thick synthetic fabric? what should be the thickness of a wool fabric (k = 0.035 w/m·°c) if the person is to achieve the same level of thermal comfort wearing a thick wool coat instead of a five-layer ski jacket?

The coefficient of friction is a number that represents the resistance to sliding between two in contact with one another.

The necleus of an atom is made up of what subatomic particles?