Energy of a Photon

1.       (a)     quantum of energy / radiation / packet of energy                                               B1

  (b)   (i)      f = E/h = 5.60 × 10–19 /6.63 × 10–34                                                         C1
f = 8.45 × 1014 (Hz)                                                                               A1

(ii)     1   minimum energy to release an electron from the surface (of the metal) B1

2   5.60 × 10–19 – 4.80 × 10–19 (= 8.0 × 10–20 J)                                        B1

(iii)    8.0 × 10–20 = ½(9.1 × 10–31)v2                                                                M1
giving v = 4.2 × 105 (m s–1)                                                                    A1

  (c)    (i)      Correct selection of: λ = h/p or λ = h/mv                                                 M1
where all symbols are defined                                                                 A1

(ii)     λ = 6.6 × 10–34 /(9.1 × 10–31 × 4.2 × 105)                                                  C1
λ = 1.7 × 10–9 (m)                                                                                  A1

[11]