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CSEC (CXC) Geometric Optics — practice questions

Explore 60 free Geometric Optics questions in CSEC (CXC) Physics. Open each question or exercise to read its content, reference answers and available explanation.

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Geometric Optics questions and exercises with answers

Showing questions 1–30 of 60.

In geometric optics, what does the word ray mean?Read the answer and worked solution →Why does light behave like a ray in almost every situation a student meets in a laboratory?Read the answer and worked solution →Which two laws govern the way light changes direction when it interacts with matter?Read the answer and worked solution →A girl stands 1.2 m in front of a flat bathroom mirror. Where is her image and what kind of image is it?Read the answer and worked solution →What is refraction?Read the answer and worked solution →Zircon has an index of refraction of 1.923. Taking the speed of light in a vacuum as 3.00 x 10^8 m/s, what is the speed of light inside zircon?Read the answer and worked solution →Fresh water has an index of refraction of 1.333. Taking the vacuum speed of light as 3.00 x 10^8 m/s, what is the speed of light in fresh water?Read the answer and worked solution →Which equation states the law of refraction for a ray crossing from medium 1 into medium 2?Read the answer and worked solution →The law of refraction is also called Snell's law. Who was Snell?Read the answer and worked solution →What is the accepted speed of light in a vacuum, to three significant figures?Read the answer and worked solution →How long does light take to travel from the Moon to the Earth, a distance of 3.84 x 10^5 km, at 3.00 x 10^8 m/s?Read the answer and worked solution →A polystyrene pipe of index 1.49 is surrounded by air of index 1.00. What is the critical angle for light travelling inside the pipe?Read the answer and worked solution →Light travels inside fresh water of index 1.333 and meets the flat surface with air above, index 1.00. What is the critical angle?Read the answer and worked solution →Diamond has an index of refraction of 2.419 and air 1.00. What is the critical angle for a diamond to air surface?Read the answer and worked solution →What is an endoscope used for?Read the answer and worked solution →An optical fibre is made of flint glass of index 1.66 clad with crown glass of index 1.52. What is the critical angle at the core to cladding boundary?Read the answer and worked solution →Light travels inside fresh water of index 1.333 and meets a layer of ice of index 1.309. What is the smallest angle at which it is totally internally reflected?Read the answer and worked solution →How much of the light falling on a good quality ordinary mirror does it reflect?Read the answer and worked solution →What is dispersion?Read the answer and worked solution →For one given transparent medium, how does the index of refraction vary across the visible spectrum?Read the answer and worked solution →Which two processes combine inside a raindrop to produce a rainbow?Read the answer and worked solution →To see a rainbow, which way must an observer face?Read the answer and worked solution →About how many colours are usually named in a rainbow, and what is the underlying distribution?Read the answer and worked solution →What is the focal length of a lens?Read the answer and worked solution →A magnifying glass held in sunlight concentrates the light to a small bright spot 8.00 cm from the lens. What are its focal length and its power?Read the answer and worked solution →A lens has a focal length of 25.0 cm. What is its power in diopters?Read the answer and worked solution →Reading glasses on a pharmacy rack are labelled 1.75 D. What is the focal length of these lenses?Read the answer and worked solution →A prescription for new eyeglasses reads -4.50 D. What is the focal length and what kind of lens is it?Read the answer and worked solution →A ray is aimed at the exact centre of a thin lens, either converging or diverging. What happens to it?Read the answer and worked solution →What makes an image a real image?Read the answer and worked solution →

Worked practice questions

In geometric optics, what does the word ray mean?

  1. A straight line that starts at some point
  2. A curved path that bends round obstacles
  3. A wavefront spreading in all directions
  4. A beam that widens steadily as it goes
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Correct answer: A. A straight line that starts at some point

1. The word ray is borrowed from mathematics, where it means a straight line that originates at some point. 2. Light is modelled as travelling along such straight lines between the places where it meets matter. 3. A ray may change direction at a mirror or at a boundary, but between those events it stays straight. 4. Curved paths and spreading wavefronts belong to the wave description, not to the ray model. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.1 The Ray Aspect of Light_

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Why does light behave like a ray in almost every situation a student meets in a laboratory?

  1. Its wavelength is about one centimetre
  2. Its wavelength is roughly one metre long
  3. Its wavelength is less than one micron
  4. Its wavelength is exactly one micron long
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Correct answer: C. Its wavelength is less than one micron

1. The wavelength of light is less than a micron, which is a thousandth of a millimetre. 2. Ray behaviour needs objects several times larger than the wavelength, and almost every object on a laboratory bench is far larger than a micron. 3. So light meets mirrors, lenses and slits of ordinary size as a ray, with only subtle wave effects. 4. A wavelength of a centimetre or a metre would put everyday objects below the wave threshold, which is not what is observed. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.1 The Ray Aspect of Light_

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Which two laws govern the way light changes direction when it interacts with matter?

  1. Dispersion and absorption
  2. Reflection and dispersion
  3. Refraction and diffusion
  4. Reflection and refraction
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Correct answer: D. Reflection and refraction

1. Two laws govern how light changes direction when it interacts with matter. 2. The law of reflection covers situations in which light bounces off matter. 3. The law of refraction covers situations in which light passes through matter. 4. Dispersion and diffusion are consequences of these two laws rather than separate governing laws. _Source: OpenStax College Physics (CC BY 4.0), Ch 25 "Geometric Optics", section 25.1 The Ray Aspect of Light_

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