The yellow sodium D lines have wavelengths of 589.0 nm and 589.6 nm. When they are used to illuminate a Michelson interferometer, it is noted that the interference fringes disappear and reappear periodically as the mirror M1 is moved. Why does this happen? How far must the mirror move between one disappearance and the next?

Which statements about tornadoes are true? check all that apply. (a) about 12,000 tornadoes hit the united states every year. (b) a tornado looks like a funnel. (c) tornadoes are deadly atmospheric storms that cause millions in damages each year. (d) tornadoes can reach wind speeds of more than 300 miles per hour. (e) kansas is the state with the most tornadoes. (f) you will always notice a funnel before a tornado strikes.