Reflection & Refraction (Edexcel IGCSE Physics)

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  • True or False?

    Visible light is a transverse wave.

    True.

    Visible light is a transverse wave.

  • True or False?

    Light can undergo reflection and refraction.

    True.

    Light can undergo reflection and refraction.

  • State the type of wave sound is.

    Sound is a longitudinal wave.

  • What is the name given to the reflection of sound waves?

    The name given to the reflection of sound waves is an echo.

  • Can sound waves be refracted?

    Yes, sound waves can be refracted.

  • State the type of wave represented by the diagram.

    A sinusoidal waveform oscillating from a crest to a trough. A double ended arrow indicates the direction of vibration at right angles to an arrow pointing to the right indicating the direction of energy transfer.

    The diagram represents a transverse wave.

  • State whether the diagram represents a light wave or a sound wave.

    Several vertical parallel lines at different distances apart have an arrow pointing to the right straight through the middle.

    The diagram represents a longitudinal wave, so it represents a sound wave.

  • Define reflection.

    Reflection is when a wave hits a boundary between two media and does not pass through, but instead stays in the original medium.

  • What does refraction mean?

    Refraction means a wave passes a boundary between two different transparent media and undergoes a change in direction.

  • What is the law of reflection?

    The law of reflection states that the angle of incidence (i) is equal to the angle of reflection (r).

  • Define the angle of incidence.

    The angle of incidence is the angle between the incoming ray and the normal.

  • What happens to light when it passes from air to glass?

    When light passes from air to glass, it slows down so it bends towards the normal.

  • How does light behave when moving from glass to air?

    When light moves from glass to air, it speeds up, so it bends away from the normal.

  • True or False?

    The frequency of light changes during refraction.

    False.

    The frequency of light does not change during refraction. The wavelength and speed of light change during refraction.

  • Define the term medium in optics.

    In optics, a medium is a material that transmits light.

  • What is a ray diagram?

    A ray diagram is a diagram used to show the direction of waves, with arrows indicating the incident and reflected/refracted rays.

  • What happens to light when passing along the normal into a transparent medium?

    When light passes along the normal into a transparent medium, it does not bend at all.

  • State why the light bends towards the normal when it passes between the boundary from air to glass as shown in the diagram.

    A light ray passes from air into glass. At the boundary, it bends more towards the normal. Upon leaving the glass the ray bends away from the normal.

    The light bends towards the normal when it passes between the boundary from air to glass as shown in the diagram because glass has a higher refractive index than air. The wave slows down and the wavelength increases.

  • Define the aim of the refraction core practical.

    The aim of the refraction core practical is to investigate the refraction of light using transparent rectangular blocks, semi-circular blocks, and triangular prisms.

  • What is the independent variable in the refraction core practical?

    The independent variable in the refraction core practical is the shape of the block.

  • What is the dependent variable in the refraction core practical?

    The dependent variable in the refraction core practical is the direction of refraction.

  • State one control variable in the refraction core practical.

    One control variable in the refraction core practical is any one from:

    • Width of the light beam

    • Wavelength of light

    • Frequency of light

  • What equipment is used to provide a narrow beam of light?

    A ray box is used to provide a narrow beam of light.

  • How is a protractor used in the refraction core practical?

    A protractor is used to measure the angles of incidence and refraction.

  • True or False?

    A sharpened pencil is used to mark angles of incidence and refraction in the refraction core practical.

    True.

    A sharpened pencil is used to accurately mark angles of incidence and refraction for the refraction core practical.

  • What is the purpose of a sheet of paper in the refraction core practical?

    The purpose of a sheet of paper is to mark the lines indicating the incident and refracted rays.

  • State a common systematic error in the refraction core practical.

    A common systematic error in the refraction experiment is an error that occurs if the normal lines are drawn incorrectly.

  • What safety consideration should be taken when using the ray box?

    A safety consideration that should be applied when using a ray box is to avoid looking directly at the light to prevent eye damage.

  • Define refractive index.

    The refractive index is the ratio of the speed of light in a vacuum and the speed of light in a material.

  • True or False?

    The refractive index has no units.

    True.

    Since the refractive index is a ratio, it has no units.

  • True or False?

    When i less than r, the refracted ray bends toward the normal.

    False.

    When the angle of incidence i is less than the angle of refraction r, or i less than r, the refracted ray bends away from the normal.

  • State the equation for the refractive index.

    The equation for the refractive index is n space equals space fraction numerator speed space of space light space in space straight a space vacuum over denominator speed space of space light space in space material end fraction

    Where:

    • n = the refractive index

  • True or False?

    The value for the refractive index of a material will always be less than the speed of light in a vacuum.

    True.

    The value for the refractive index of a material will always be less than the speed of light in a vacuum.

  • What trigonometric function is used in Snell's law?

    The trigonometric function used in Snell's Law is sine.

  • True or False?

    When i greater than r, the refracted ray bends toward the normal.

    True.

    When the angle of incidence i is greater than the angle of refraction r, or i greater than r, the refracted ray bends toward the normal.

  • State the equation for Snell's law in terms of refractive index.

    The equation for snell's law in terms of the refractive index is n space equals space fraction numerator sin space i over denominator sin space r end fraction

    Where:

    • n = refractive index of the material, which has no units

    • i = angle of incidence, measured in degrees (°)

    • r = angle of refraction, measured in degrees (°)

  • State the angle of incidence shown in the diagram.

    A ray is incident at the boundary between air and glass at an angle of 39 degrees to the normal. The ray leaves the air-glass boundary at an angle of 25 degrees to the normal.

    From the diagram, the angle of incidence is 39°.

  • State the angle of refraction shown in the diagram.

    A ray is incident at the boundary between air and glass at an angle of 39 degrees to the normal. The ray leaves the air-glass boundary at an angle of 25 degrees to the normal.

    From the diagram, the angle of refraction is 25°.

  • State the aim of the Snell's law core practical.

    The aim of the Snell's law core practical is to investigate the refractive index of glass using a glass block.

  • What is the independent variable in the Snell's law core practical?

    The independent variable in the Snell's law core practical is the angle of incidence (i).

  • What is the dependent variable in the Snell's law core practical?

    The dependent variable in the Snell's law core practical is the angle of refraction (r).

  • State one control variable in the Snell's law core practical.

    One control variable in the Snell's law core practical is any one from:

    • use of the same glass block

    • same light beam width

    • same frequency

    • the same wavelength of light

  • Define Snell's law.

    Snell's law is the ratio of the sine of the angles of incidence and refraction.

  • What equipment is used to measure angles in the Snell's law core practical?

    A protractor is used to measure the angles of incidence and refraction in Snell's law core practical.

  • How is the refractive index determined in the Snell's law core practical?

    The refractive index is determined by plotting a graph of sin(i) versus sin(r ) graph and finding the gradient.

  • What is a common source of systematic error in the Snell's law core practical?

    A common source of systematic error in the Snell's law core practical is drawing the normal lines incorrectly.

  • What safety measures should be taken when using the ray box in the Snell's law core practical?

    The safety measures that should be taken when using the ray box in Snell's law core practical are to avoid looking directly at the light to prevent eye damage.

  • Light is incident from the air into a glass block. State whether the angles of refraction indicated will be larger or smaller than the angles of incidence.

    The angles of refraction will be smaller than the angles of incidence because glass has a higher refractive index than air.

  • Define the term critical angle.

    The critical angle is the angle of incidence that gives an angle of refraction of exactly 90°.

  • When does total internal reflection (TIR) occur?

    Total internal reflection (TIR) occurs when the angle of incidence is greater than the critical angle, and the ray is travelling from a denser material into a less dense material.

  • How is total internal reflection used in communications?

    Total internal reflection is used to transmit information through optical fibre cables for television and internet communications.

  • State the equation for the critical angle in terms of the refractive index.

    The equation for the critical angle in terms of the refractive index is n space equals fraction numerator 1 over denominator sin space c end fraction

    Where:

    • n = refractive index, which has no units

    • c = critical angle, measured in degrees (°)

  • Name one application of total internal reflection.

    One application of total internal reflection is any one from:

    • periscope

    • optical fibre

  • True or False?

    Total internal reflection can occur when light travels from a less dense medium into a denser medium.

    False.

    Total internal reflection only occurs when light travels from a denser material into a less dense material.

  • Describe what happens to the ray of light at the glass-liquid boundary at X in the following diagram.

    A ray incident on a glass-liquid boundary has an angle of 65 degrees to the normal. The subsequent ray leaving the boundary has an angle of 65 degrees to the normal.

    The behaviour of the light ray at the glass-liquid boundary at X is defined as total internal reflection (TIR).

  • Identify the diagram where the angle of incidence equals the critical angle.

    Each diagram shows different angles into and out of the glass-air boundary of a semi-circular block to the normal. Diagram 1 angle i to r. Diagram 2 angle c to a ray along the boundary. Diagram 3 angle i to angle r.

    The second diagram shows the angle of incidence i equal to the critical angle c.