Describe how to investigate the reflection of light by a plane mirror.

Stand the mirror on a line drawn on paper and draw a normal to it, shine a narrow ray from a ray box at the point where the normal meets the mirror and mark each ray with crosses, then remove the mirror, draw the rays and measure the angles of incidence and reflection from the normal with a protractor.

Describe how to investigate the refraction of light through a rectangular glass block.

Draw round the block on paper, shine a narrow ray from a ray box into one side at an angle and mark the entering and emerging rays with crosses, then remove the block, join the points to draw the ray through it, draw the normals and measure the angles of incidence and refraction with a protractor.

Why is a narrow ray of light used when tracing rays through a glass block?

The centre of a narrow ray can be marked more exactly, so the drawn ray and the angles measured from it have a smaller uncertainty.

Why are the crosses marking the path of a ray placed as far apart as possible?

A line drawn through widely spaced points has a more exact direction, so small errors in placing the crosses make less difference to the measured angle.

OCR GCSE Combined Science Physics J250

Electricity

Topic overview Charge, and producing static electricity Transfer of electrons in charging and discharging Current as a rate of flow of charge Charge, current and time Series and parallel circuits, and circuit symbols Current, potential difference and resistance Resistors whose resistance changes, and investigating them Linear and non-linear circuit elements from graphs Net resistance in series and parallel Circuits for measurement, and electrical power

Energy

Topic overview Conservation of energy, and energy stores Energy changes on heating, and calculating them Energy of a moving body, a spring and a raised object Dissipation, and energy transfer in domestic devices Power ratings, and calculating efficiency Reducing unwanted energy transfer, and the rate of cooling

Forces

Topic overview Measuring distance and time, and calculating speed Converting units, and rates Vectors and scalars in motion Distance-time and velocity-time graphs Average speed, and the equations of uniform motion How objects interact, and forces as vectors Newton's first law Newton's second law Work done, and stored energy Power, and Newton's third law Stretching, bending and compressing; elastic and plastic Force and extension, linear and non-linear The spring constant, and work done in stretching Gravitational fields, weight and free fall Calculations with weight and gravitational field strength

Global Challenges

Topic overview Typical speeds and everyday accelerations Reaction time, stopping distance and the dangers of large decelerations Stopping distance, acceleration and collision force calculations Energy resources, and trends in their use The national grid, and step-up and step-down transformers Why the national grid is efficient, and power in a transformer Mains electricity: a.c., d.c. and the domestic supply Live, neutral and earth wires, and electrical danger

Magnetism and Magnetic Fields

Topic overview Permanent and induced magnets, and magnetic poles Magnetic fields, and the dipping compass The magnetic effect of a current, and solenoids

Matter

Topic overview How the atomic model changed, and the structure of the atom The size of atoms, and defining density Density of the states of matter, and density calculations Conservation of mass in changes of state Heating a system, and specific heat capacity Calculations with specific heat capacity and latent heat Gas molecules, temperature and pressure

Radioactivity

Topic overview Protons, neutrons and isotopes Unstable nuclei and the emissions they give out Balancing nuclear equations Electron energy levels, and radiation from atoms Half-life and the randomness of decay Penetration of alpha, beta and gamma Contamination and irradiation, and reducing the hazard

Waves in Matter

Topic overview Amplitude, wavelength, frequency and period The wave equation Transverse and longitudinal waves Modelling waves with ripples and sound Electromagnetic waves as transverse, and energy transfer Frequency and wavelength across the spectrum What our eyes detect, and light as an electromagnetic wave Uses of electromagnetic waves Hazards of ultraviolet, X-rays and gamma rays Investigating reflection and refraction of light

Waves in Matter

Investigating reflection and refraction of light

3 things to know
Paper 6 (Physics)

Overview

Investigating reflection by a plane mirror and refraction through a rectangular glass block with a ray box, why a narrow ray and widely spaced crosses give better angles, working safely in a darkened room, the independent and dependent variables, and the spectrum a prism produces.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Process

In an investigation of refraction through a glass block, which is the independent variable and which is the dependent variable?

Process

Why are ray-tracing experiments carried out in a darkened room?

Process

Give a safety precaution when using a ray box.

Questions from this subtopic

Each one with the model answer underneath.

1
Describe how to investigate the reflection of light by a plane mirror.
Model answer
Stand the mirror on a line drawn on paper and draw a normal to it, shine a narrow ray from a ray box at the point where the normal meets the mirror and mark each ray with crosses, then remove the mirror, draw the rays and measure the angles of incidence and reflection from the normal with a protractor.
2
Describe how to investigate the refraction of light through a rectangular glass block.
Model answer
Draw round the block on paper, shine a narrow ray from a ray box into one side at an angle and mark the entering and emerging rays with crosses, then remove the block, join the points to draw the ray through it, draw the normals and measure the angles of incidence and refraction with a protractor.
3
Why is a narrow ray of light used when tracing rays through a glass block?
Model answer
The centre of a narrow ray can be marked more exactly, so the drawn ray and the angles measured from it have a smaller uncertainty.
4
Why are the crosses marking the path of a ray placed as far apart as possible?
Model answer
A line drawn through widely spaced points has a more exact direction, so small errors in placing the crosses make less difference to the measured angle.
5
Why are ray-tracing experiments carried out in a darkened room?
Model answer
So that the ray from the ray box shows up clearly on the paper and can be marked accurately.
6
Give a safety precaution when using a ray box.
Model answer
Do not touch the lamp housing while it is switched on or just afterwards, because it becomes hot enough to burn.

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