Planning Experiments for A-Level Physics

[Sati]

Hi,
Please accept my warm greetings.
I want some help concerning practical physics, more precisely planning exercises at A-level.
I feel at a loss each time I have to tackle such a question.
I find it difficullt to determine the dependent and independent variables and plan the procedure.
Please kindly help me by providing some tips or general guidelines on how to approach a certain question.
I'll be really grateful.
Thanks.

[Open Intelligence]

(a) Measure the thickness of the glass by using a micrometer screwgauge

(b) Place a piece of glass between a UV lamp and a piece of film.

(c) The film is then developed and placed between an incandescent source and the lightmeter.

(d) The lightmeter gives the degree of UV absorption by the glass.

(e) Repeat the experiment by using different thicknesses of glass.

(f) Draw a well-labelled diagram showing all the equipment and their location.

(g) Plot of graph of value on lightmeter (y) against thickness of glass

Special precautions to take to get reliable results:
(i)   keep the exposure time the same for different thicknesses of glass
(ii)  the distance between the light source and the film must be kept constant each time the experiment is repeated.
(iii)  keep the intensity of the UV source constant
(iv) carry out the experiment in a dark room

Special safety precautions:
(i)  UV light is dangerous to the eyes so safety goggles must be worn.
(ii) Perform experiment away from extraneous sources of UV.

The sentences in bold are those which are common to all practical physics experiments.

The independent variable (x-axis) is the quantity which you are able to control or vary in the experiment. Here it is the thickness of glass. The value of the lightmeter (dependent variable, y-axis) depends on the thickness of the glass used.