RP 2 : youngs double slit experiment

Question 1

what is the overall aim of this experiment?

Answer 1

• investigate relationship between slit screen distance (D) and fringe width (w)

Question 2

what are the variables in this experiment?

Answer 2

• independent variable is distance between the slits and screen
• dependent variable is the fringe width
• control variables are the wavelength of laser and slit seperation

Question 3

what is the general method for this experiment?

Answer 3

• set up apparatus, by fixing laser and slits to a restort stand and place screen so that D is 0.5m, measured using metre ruler
• darken room turn on laser
• measure from central fringe width across many fringes using vernier callipers and divide by number of fringe widths
• increase D by 0.1m, repeat until 1.5
• repeat twice more and calc mean w for each D

Question 4

what do we plot in this experiment?

Answer 4

y = mx + c

and w = Dwl/ s

m = lambda / s

y = w. x = D

Question 5

how do we calculate wavelngth from this graph

Answer 5

so gradient = lambda / s

gs = lambda

Question 7

how can we avoid parallax error?

Answer 7

• make sure screen and double slit are aligned perfectly