Which of the following observations led bohr to formulate his model of the hydrogen atom? a. neutrons form a diffraction pattern when scattered from a nickel crystal. b. the peak of blackbody radiation moves to shorter wavelengths as temperature increases. c. a low-density gas emits a series of sharp spectral lines. d. electrons are observed to have wave nature.

•• al and bert are jogging side-by-side on a trail in the woods at a speed of 0.75 m/s. suddenly al sees the end of the trail 35 m ahead and decides to speed up to reach it. he accelerates at a constant rate of 0.50 m/s2, while bert continues on at a constant speed. (a) how long does it take al to reach the end of the trail? (b) once he reaches the end of the trail, he immediately turns around and heads back along the trail with a constant speed of 0.85 m/s. how long does it take him to meet up with bert? (c) how far are they from the end of the trail when they meet?

The energy of a photon was found to be 3.38 × 10–19 j. planck’s constant is 6.63 × 10–34 j • s. which color of light corresponds to this photon?

What is the coefficient of kinetic friction μk between the block and the tabletop?