Question one
- You are provided with the following apparatus
- A lens
- Lens holder
- Candle
- Screen
- A screen with a hole having cross-wire
- Metre rule
Proceed as follows- Set up the apparatus as in the figure below with distance S = 42cm
Without changing the distance S move the lens slowly away from cross-wires until a sharp enlarged inverted image is formed on screen position L1. Measure the distance U1 from cross-wires to the lens and record this value in table 2. Keeping distance S, constant move the lens away from cross-wires to a new position L2 where a small sharp inverted image is formed on the screen. Measure the new object distance U2 and record in table 2. Determine the displacement d of the lens from L1 to L2 (i.e d = L2 – L1) - By setting the distance S to distances 44, 46, 48, 50 and 52cm as shown in table 2 repeat procedure (a). Measure and record the corresponding values of U1 and U2 in table 2
Table 2 (10mks)
S (cm)
42
44
46
48
50
52
U1 (cm)
U2 (cm)
d (U2 – U1) (cm)
d2 (cm2)
S2 (cm2)
S2 – d2 (cm2)
-
- Plot graph of S2 – d2 against S (5mks)
- Determine the slope of the graph (3mks)
- Given that S2 – d2 = 4fS, use your graph to determine the focal length of the lens (2mks)
- Set up the apparatus as in the figure below with distance S = 42cm
QUESTION TWO
- You are provided with the following:
- a metre rule;
- a retort stand, a boss and clamp;
- three pieces of thread;
- 200m1 of a liquid in a 250ml beaker labelled W;
- 200m1 of a liquid in a 250m1 beaker labelled L;
- Two masses labelled m1 and m2.
Proceed as follows:- Suspend the metre rule so that it balances at its centre of gravity G and record its value
G = .................................................................................cm (½mk) - Position mass m2 at a distance x = 5 cm from the centre of gravity G and adjust the position of ml so that the metre rule balance at G. Record the x1 of m1 from the point G in table 2.
- While maintaining the distance x = 5cm, immerse m2 completely in water. Adjust the position of m1 until the metre rule balances again (see figure 2(b)).
Record the new distance x2. - Still maintaining the same distance x = 5cm, remove the beaker, W with water and replace it with the beaker L with the liquid. Immerse m2 completely in the liquid. Adjust the position of ml until the metre rule balances again (see figure 2(c)). Record the new distance x3.
- Remove mass m2 from the liquid and dry it with a tissue paper.
- With the metre rule still suspended from its centre of gravity G, repeat the procedure in (b), (c), (d) and (e) for other values of x given in table 2. Complete the table.
TABLE 2
Distance x (cm)
Distance x1 (cm)
Distance x2 (cm)
Distance x3 (cm)
L0 = (x1 – x2)
(cm)
L1 = (x1-x3)
(cm)
5
10
15
17
20
- Plot a graph of L0(y-axis) against L1 (5mks)
- Find the slope S of the graph. (3mks)
- Find the value of k given that L1 = 25/K (2mks)
- Suspend the metre rule so that it balances at its centre of gravity G and record its value
MARKING SCHEME
-
-
S (cm)
42
44
46
48
50
52
U1 (cm)
16.0
15.0
15.0
14.0
14.0
13.0
(3mks)
U2 (cm)
25.0
28.0
31.0
33.0
36.0
38.0
(3mks)
d = (U2 – U1) (cm)
9.0
13.0
16.0
19.0
22.0
25.0
(1mk)
d2 (cm2)
81
169
256
361
484
625
(1mk)
S2 (cm2)
1764
1936
2116
2304
2500
2704
(1mk)
S2 – d2(cm2)
1683
1767
1860
1943
2016
2079
(1mk)
(10mks)
(48 – 44)cm 4 (3mks)- S2 – d2 = 4fs
y = nx
4f = slope
f = slope = 43.75 = 10.9cm
4 4 (2mks)
- S2 – d2 = 4fs
-
-
- G = 50.0 + 1cm ü ½MK (49.0 – 51.0) ----MUST BE IN 1dp
x (cm)
x1 (cm)
x2 (cm)
x3 (cm)
L0 (cm)
L1 (cm)
5.0
10.0
8.0
8.5
2.0
1.5
10.0
21.0
18.0
19.0
3.0
2.0
15.0
31.0
27.0
28.0
4.0
3.0
17.0
35.5
31.0
32.0
4.5
3.5
20.0
42.0
36.0
37.5
6.0
4.5
ü ½ each
ü ½ each
ü ½ each
ü ½ max of 1mk
ü ½ max of 1mk Total 9½mks
-
- G = 50.0 + 1cm ü ½MK (49.0 – 51.0) ----MUST BE IN 1dp
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