Update Unit 3: Physics.md

Grade 10/Science/SNC2DZ/Unit 3: Physics.md

@@ -55,10 +55,6 @@
 |Triboluminescence|- The production of light from **friction** as a result of scratching, crushing, or rubbing certain cystals<br>- Examples include: <br>- Rubbing twoquartz crystals together will produce light due to triboluminescence|<img src="https://i.ytimg.com/vi/MzBXXmcaf2M/maxresdefault.jpg" width="300">|
 |Light-Emitting Diode (LED)|- light produced as a result of an electric current flowing in **semiconductors**. <br>- **semiconductors** are materials that allow an electric current to flow in only one direction<br>- When electricity flows in the allowed direction, the LEd emits light<br>- **Does not** produce much **heat** as a by-product, nor require a **filament**, and is more energy efficient<br>- Examples include<br>- LED lights<br>- christmas tree lights<br>- illuminated signs<br>- traffic lights|<img src="https://d114hh0cykhyb0.cloudfront.net/images/uploads/rgb-fast-color-changing-led01.jpg" width="300">|
 
-
-
- - Things that emit light fill in here plz thanks
-
 ### Rays
  - Light path can be tracked via arrrows
  - `Normal`: Perpendicular line to an interface (e.g., mirror, medium boundary), intersecting where light reflects off
@@ -145,4 +141,31 @@
     - Reflected ray grows brighter as we reach critical angle, and refracted ray grows dimmer
  - **Higher** index of refraction = **lower** critical angle
 
-<img src="https://www.physicsclassroom.com/Class/refrn/u14l3b2.gif" width="500">
+<img src="https://www.physicsclassroom.com/Class/refrn/u14l3b2.gif" width="500">
+
+## Lens
+
+### Thin lens equations
+ - Can be used to find **location** and **magnification** of images
+
+$`\frac{1}{d_{o}} + \frac{1}{d_{i}} = \frac{1}{f}`$
+
+ - $`d_{o}`$: Distance of **object** from optical centre, always positive
+ - $`d_{i}`$: Distance of **image** from optical centre
+    - If positive, image is **real** and on the **opposite** side of the lens as the object
+    - If negative, image is **virtual** and on the **same** side of the lens as the object
+ - $`f`$: Distance of **focus** from optical centre
+    - Is positive in a converging lens
+    - Is negative in a diverging lens
+
+$`M = \frac{h_{i}}{h_{o}} = -\frac{d_{i}}{d_{o}}`$
+
+ - $`h_{o}`$: Height of object
+ - $`h_{i}`$: Height of image
+    - If positive, image is **upright and virtual**
+    - If negative, image is **virtual** but on the same side of the lens as the object
+ - $`M`$: Magnification of image
+    - If positive, image is **upright and virtual**
+    - If negative, image is **inverted and real**
+    - If greater than 1, image is larger and farther from the optical centre than the object
+    - If less than 1, image is smaller and closer to the optical centre than the object