Estimate the effective temperature of the sun from the fact that the human eye is sensitive to light in the range 400-700 nm (1nm = 10^-9m). hint: use wien's law.
the book used is "astrophysics in a nutshell" by dan maoz

Agroup of students is studying convection currents. they fill two identical balloons with the same amount of helium. one balloon is placed in a freezer and the other in an area with warm air. after 10 minutes, the balloons are released from a height of 1 meter. which of the following do the students most likely observe? question 2 options: the balloons rise at the same rate. both balloons are the same size. the ballons both rise. the cold ballon is larger than the warm balloon. the cold balloon expands and rises. the warm balloon shrinks and sinks. the warm balloon expands and rises. the cold balloon shrinks and sinks.

If jason ii needs 15 kw of power at 300 volts to operate, what amperage of current must flow through the cable?

Why does lightning travel from clouds to the ground? a. the negatively charged ground attracts the positive charge from the clouds b. charges are exchanged between negatively charged clouds and positively charged ground c. gravity pulls the negatively charged energy from clouds downward d. gravity pulls the positively charged energy from clouds downward