Mark scheme for questions on Radioactivity

answers to questions on med phys

Refraction

Homework on Gases

1.       (a)     An explanation to include:

          1. moving gas particles;
2. hitting container walls;
[Allow bouncing off the sides for 2 marks]
[Ignore vibrating/collisions with other particles]                                      2

  (b)   increases;
increases;
stays the same;
stays the same;                                                                                                 4

  (c)    (i)      increases;
in proportion/                                        2

(ii)     correctly indicated – intercept with horizontal axis;                                1

(iii)    zero/minimum;                                                                                        1

[10]

 

  2.     (a)     four points plotted correctly;;
4/3 correct       -    2 marks
2    correct       -    1 mark
straight line drawn;                                                                                           3

(b)     –260 to –280;;
[Allow an answer between +260 – +280 for 1 mark]                                           2

  (c)   impossible temperature/this is below absolute zero/pressure is
zero/no movement;                                                                                           1

(d)     (i)      273;                                                                                                         1

(ii)     –196;;
[Allow 77-273 for 1 mark]                                                                      2

[9]

 

  3.     (a)     (i)      (particles) collide with tyre wall;

Ignore push/pushing

          this produces a force;                                                                              2

  (ii)   more collisions (/sec);                                                                             1

(b)     correct conversion into K;

           = P2;

          1.72 × 105 = P2;                                                                                                3

for 2 marks accept any one of

2.08 × 105

temps swopped over (1.68 × 105)

for 1 mark accept 1.39 × 105

units if seen must be correct
do not accept 1.7 unless the working is shown

[6]

 

4.       (a)     (i)      particles collide with/hit/bounce off (container) wall/eq;                         1

(ii)     An explanation to include:

          1. greater volume/space/room;
2. fewer/less collisions (with container);                                        2

  (b)   (i)      increases/eq;                                                                                            1

(ii)     increases/eq;                                                                                            1

[5]

 

5.       (a)     (102 + 273 =) 375;                                                                                           1

  (b)

	decreases	Stays the same	increases but does not double	doubles
temperature of gas					1
pressure of gas					1
kinetic energy of particles					1

                                                                                                                        ;;;

  (c)   collisions;                                                                                                         1
with walls etc;                                                                                                   1

[6]

 

 

 

 

Uses of Total Internal Refection.