7a) Use diffraction grating formula of n= 2 for two different wavelengths. Angular separation is the difference between the two angles of the second order. Second order separation is larger than first order but the intensity is lower. To find highest order assume 90 deg. Find the n value. Select a whole number below the calc n. Use the larger wavelength for this calc.
8. Use ratio as the p.d is proportional to length. b) Again use direct proportionality to find new e.m.f of battery. To find the internal resistance , use the resistor to draw current from the battery and measure the p.d of battery terminals . The internal resistance can be calc as the e.m.f and p.d is known. Use E = V + Ir where I = p.d/R. The resistor is added in parallel to the battery.
