Mantles for gas lanterns contain thorium, because it forms an oxide that can survive being heated to incandescence for long periods of time. Natural thorium is almost 100% 232 Th , with a half-life of 1.4051010 y . If an average lantern mantle contains 300 mg of thorium, what is its activity?
Modern Cosmology (PHYS 3040) M/W 1. Waves a. a disturbance in some quantity(space and time) that propagates in a regular way i. Characteristics -crests and troughs (amplitudes) -frequency and wavelength(lambda) “time series” one particular thing throughout time “snapshot” data captured at one moment in time ii. Longitudinal Waves a. a wave going in one direction but the disturbance is along the same direction ex. Sound wave iii. Transverse a. an oscillation moving in one direction Ex. Doing “the wave” in a stadium where everyone stands up, raises their arms and sits down b. Types of Waves Reflection i. wave train travels in opposite direction Law of Reflection= the incident angle is equal to the reflective angle Refraction i. change in wave speed in a medium and change in direction (the incident angle is different than the reflective angle) ex. When you stick a pencil into a cup filled with water, it looks as if the pencil is bending Diffraction i. light waves that bend around edges ex. Light behind a screen through a slit, the area of light diffuses out Interference i. constructive or destructive superposition of waves a