MODERN PHYSICS

A photon emitted from an excited hydrogen atom has an energy of 3.02 electron volts. Which electron energy-level transition would produce this photon?

A. n=1 to n=6

B. n=2 to n=6

C. n=6 to n=1

D. n=6 to n=2

I chose B but the correct answer is D can someone tell me why? And what's the difference?

Acar accelerates from 5.0 m/s to to 11 m/s at a rate of 3.0 m/s^2. how far does it travel while accelerating? 20m 117m 43m 16m

Aroll in a paper machine is powered by a separately excited dc machine. operating point 1 (under load): the roll typically operates at 764 rpm and must provide 301 nm of torque to oppose the load of the paper. the armature voltage is 230v for this operating point operating point 2 (no load): when the load is removed the speed of the roll increases to 900 rpm (the field characteristics are unchanged) la ea dev m (a) calculate the maximum torque (units of nm) that the motor can supply with this applied voltage (b) calculate the value of the armature resistance, ra (in ohms) (c) at operating point 1 (loaded condition), the field current, i, and the total input power (armature field), are measured to be to be 10 a and 28,600 w respectively. use this information to calculate the value of the field resistance, rf (in ohms). (d) (d) at operating point 1 (loaded condition), calculate the motor efficiency. express your answer as a percent to at least 2 significant digits. (d) if the field voltage is reduced by 1/2, calculate the new stall torque (in nm) of the motor (f). if the field voltage is reduced by 1/2, calculate the new no-load speed (in rad/sec)

Sound is a disturbance that travels through a medium as a