How do you find the total number of nodes in a two-source interference pattern? I know the formula is like Na=d/lambda but apparently, according to my physics teacher, you have to go one step further to find the total number of nodes. But he never showed us how, and I cant find anything online.

Like for example if the distance between the two sources was 20cm and the wavelength was 2cm, then it would be 20/2=10 right? But my teacher said its wrong. And he wont explain why.

I have a test on this tomorrow please help

Amoving company collects data about couches they move and displays the data in a table. the force along the ramp, the angle of the ramp, and the height the couch is raised to are shown. which statements correctly compare the work done to move the couches? check all that apply. the same amount of work is done for couches 1 and 3. the same amount of work is done for couches 2 and 3. the work for couch 1 is greater than the work for couch 2. the work for couch 2 is less than the work for couch 3. the work for couch 3 is greater than the work for couch 1. the work for couch 2 is greater than the work for couch 1.