IB Physics SL C.3.3 Refractive Index

Practise calculating refractive index from light speed or refraction data, comparing materials and linking a change in speed to wavelength while frequency remains unchanged.

Exam points

calculate absolute refractive index with n = c/v and check that an ordinary material gives n at least one
derive relative refractive index from a ratio of sines or wave speeds across the boundary
calculate wavelength in a medium from λ = λ₀/n while keeping the source frequency fixed

[Maximum number: 2]

A group of students is investigating refraction in a semi-circular glass block.

Light from a ray box enters the curved side of the block. The light passes through the block and leaves, refracted, at P .

They plot a graph of the variation with the sine of $\theta_{i}$ of the sine of $\theta_{r}$ .
They add uncertainty bars for $\sin \theta_{r}$ for the first and last data point and draw the best-fit line.

$Figure for Question C.3.3—Refractive index question 1 — IB Physics SL$

Determine the value of the refractive index of the glass with its absolute uncertainty.

States gradient gives the value of the refractive index

OR

n=1.5 $n=1.5 \pm 0.2$

MP1 can be shown as an equation.

Candidates may calculate the uncertainty by using the gradient of the line found in cii) or finding the average of the max and min lines of best fit.

Look for working leading to $0.1 \leq \Delta n \leq 0.2$ .

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