(c) sin72 = 1.80sin θ Correct answer on its own gets both = 31.895 = 31.9 correct answer >= 2sf seen θ Do not allow 31 for second mark Allow 31.8 32 − 2 (d) 1.80 sin OR θc=1.40 = 51.058 = 51.1 ° (accept 51) θc Correct answer on its own gets both marks Don’t accept 50 by itself 2 OR = 0.778 (e) (i) 22 + their (c) (22 + 31.9 = 53.9) 53.9 > (51.1) critical angle If c + 22 < d then TIR expected If c + 22 > d then REFRACTION expected OR c + 22 < d (θc ) ecf from (c) and (d) angle less than critical angle max 1 for because angle > critical angle’ only if their d > c ‘TIR + 22 2 (ii) TIR correct ecf from e(i) for refraction answer Tolerance: horizontal line from normal on the right / horizontal line from top of lower arrow. If ei not answered then ecf (d). If ei and d not answered then ecf c 1 [11] π M2.(a) (i) / 2 (radians) or 90 (degrees) No path differences Penalise contradictions No fractions of a cycle 1
(c) sin72 = 1.80sin θ Correct answer on its own gets both θ = 31.895 = 31.9 correct answer >= 2sf seen Do not allow 31 for second mark Allow 31.8 − 32 2 (d) 1.80 sin θc=1.40 OR θc = 51.058 = 51.1 ° (accept 51) Correct answer on its own gets both marks Don’t accept 50 by itself 2 OR = 0.778 (e) (i) 22 + their (c) (22 + 31.9 = 53.9) 53.9 > (51.1) critical angle If c + 22 < d then TIR expected If c + 22 > d then REFRACTION expected OR c + 22 < d (θc ) ecf from (c) and (d) angle less than critical angle max 1 for ‘TIR because angle > critical angle’ only if their d > c + 22 2 (ii) TIR correct ecf from e(i) for refraction answer Tolerance: horizontal line from normal on the right / horizontal line from top of lower arrow. If ei not answered then ecf (d). If ei and d not answered then ecf c 1 [11] M2.(a) (i) π / 2 (radians) or 90 (degrees) No path differences Penalise contradictions No fractions of a cycle 1
AS-Waves-and-Optics.docx