Important Notes for CBSE Class 7 Science Chapter 15 – Light. Light Class 7 Notes and Study Material Download in PDF form.
Light Notes | Light Class 7 Notes | Light Quick Revision | Light Class 7 Quick Revision Notes | Science Class 7 Ch 15 Notes | NCERT Class Class 7 Science Chapter 15 Notes PDF.
Light Class 7 Notes
Light travels in a straight line:
- To understand this a small experiment is conducted in which one has to observe flame of a candle using a straight pipe and then with a bent pipe.
- One can only see light appearing from the straight pipe.
LAWS OF REFLECTION:
- When light falls on a shiny or polished surface light gets reflected.
- Reflection of light can be used to change the direction of light.
- Stainless steel, mirrors, clear water can serve as polished surface.
- Picture of an object generated due to reflection of light in mirror is called image.
- Object is any material or item which on reflection of light can form an image.
- Upright image is called erect.
- Image formed in plane mirror is upright and similar in size of the object.
Left or right in mirrors:
- In mirrors left appears as right and right appears as left.
- Side of image get interchanged and it does not become inverted.
SPHERICAL MIRRORS:
- This is a curved mirror whose shape is spherical and can have either concave or convex shape.
- If reflecting surface of sphericalmirror is concave, it is called a concavemirror.
- The concave mirror forms image which is smaller or larger in size than the object.
- The image may be real or virtual.
- Concave mirrors are used by doctors to check eyes, ears, nose, throat, teeth
- The reflectors of torches, headlights of cars and scooters are concave mirror.
- If the reflecting of spherical mirror is convex,then it is a convex mirror.
- If image can be observed on screen, it is called as real image
- If image cannot be observed on screen, it is called as virtual image.
IMAGES FORMED BY LENSES:
- Magnifying glass is a type of lense.
- Lenses used to make spectacles,telescopes and microscopes.
- Convex lenses: lense which are thick in middle and edges are thinner.
- Convex lens forms a real, inverted and diminished image.
- These are converging lenses used in magnifying glasses
- Concave lenses: lense which is thinner in the middle as compared to the edges.
- Concave lens always forms a virtual, erect and diminished image.
- They are also called as diverging lens and used to make camera lenses and binoculars.
SUNLIGHT — WHITE OR COLOURED?
- Sunlight is composed of seven colors.
- These colors red, orange, yellow, green, blue, indigo and violet.
- Together they appear as white light.
- The white light if passed through a prism split into seven colors, it is called dispersion.