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Refraction & Reflection Curriculum based on Secondary students

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Aim To learn how surfaces refract and reflect the ray of light. The application and uses of refraction and reflection in everyday life.

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Objective Students should be able to understand and apply the terms outlined and the nature of reflection and refraction of light. Students should be able to use a ray model to describe the behaviour of light.

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Terms which should be known Incident Ray Refracted Ray / Reflected ray Laws of Refraction / Laws of Reflection Critical Angle & Refractive Index Real Image Virtual Image Concave/Convex (Focal length)

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Incident Ray Is a ray of light that strikes a surface. The angle between this ray and the perpendicular or normal to the surface is the angle of incidence.

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Reflective and Refractive Ray

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Refracted Ray Is a ray of light that passes through a surface to create the image. The angle between this ray and the perpendicular or normal to the surface is the angle of refraction.

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Reflected Ray Is the ray of light that is reflected by the surface. The angle between the incident ray and the normal is the same as the angle between the normal and reflected ray.

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Laws of Refraction 1. (Snell's Law) Sin i/sin r is constant. This constant is known as the refractive index of the medium, and is denoted by n. 2. The incident ray, the normal and the refracted ray are all on the same plane.

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Laws of Reflection 1. The angle of incidence is equal to the angle of reflection. 2. The incident ray, the normal and the reflected ray all lie in the same plane.

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Critical Angle & Refractive Index The usual value of refractive index refers to light going from air to a substance. If the direction of the light ray is reversed, then i and r are interchanged, and the refractive index becomes the reciprocal of the conventional value, e.g., If ang is 1.5, then gna is 1/1.5 = 0.67. These reciprocal vales are needed for deducing the relationship between refractive index (n) and critical angle (c), which is: c = sin -1 (1/n)

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Real Image Is an image in which the outgoing rays from a point on the object pass through a single point.

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Virtual Image Is an image in which the outgoing rays from a point on the object always intersect at a point.

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Concave/Convex (Focal length) It is important to be able to draw ray diagrams showing the formation of images by lenses and mirrors and to be able to calculate values of unknowns, using 1/p + 1/q = 1/f and f1/p + f2/q = 1 Concave: reflectors in torches; spotlights & projectors; dentists' mirrors and shaving mirrors. Convex: gives a wide field of view in supermarkets and inside buses.

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Rationale Different teaching methodologies we have obtained. Investigative approach (hands on). Engaging the students in every lesson because science is interesting. Essentialism, Progressivism and Reconstructivism are the philosophical ideas we will use when teaching. Combining ICT with the lessons as a natural way of learning.

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The use of ICT Use the internet as one example of ICT in the class – students research the refractive index of different materials Use data projector and laptop or smart board to play the following song which explains reflection and refraction and the uses of each http://www.haverford.edu/physics/songs/snel l.htm http://www.haverford.edu/physics/songs/snel l.htm

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Relating to real life. Telescopes Opticians Microscope Cameras Projectors...the list can go on and on...

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Sec 19.1. Review of Law: the angle of reflection is equal to the angle of incidence We use ray diagrams to show how light rays change direction when.

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