In a double-slit experiment, electrons are fired at an opaque barrier having two small slits, and a screen beyond the barrier records where the electrons hit. after many electrons are fired, what is observed on the screen?

a. the pattern observed indicates that electrons struck only the areas of the screen directly across from the two slits.

b. the pattern observed indicates that electrons struck the screen directly across from the two slits and the center of the screen

c. the pattern observed indicates that electrons struck only the center of the screen.

d. the pattern observed indicates that electrons struck the screen in alternating bands across the screen.

If the work required to stretch a spring 3 ft beyond its natural length is 15 ft-lb, how much work is needed to stretch it 27 in. beyond its natural length?

On a horizontal frictionless surface, a small block with mass 0.200 kg has a collision with a block of mass 0.400 kg. immediately after the collision, the 0.200 kg block is moving at 12.0 m/s in the direction 30° north of east and the 0.400 kg block is moving at 11.2 m/s in the direction 53.1° south of east. use coordinates where the +x-axis is east and the +y-axis is north.(a) what is the total kinetic energy of the two blocks after the collision (in ) what is the x-component of the total momentum of the two blocks after the collision? (indicate the direction with the sign of your ) what is the y-component of the total momentum of the two blocks after the collision? (indicate the direction with the sign of your answer.)

Estimate of the number of stars in our galaxy