Summary of what I learnt (Reflection)

Light is a form of energy that could be obtained from a luminous source or reflected off a non-luminous source into our eyes. When a ray of light strikes any surface, it will reflect and changes its direction of travel.

Terms used for reflection of light:

Incident ray: ray of light that strikes the surface

Reflected ray: Ray of light that is reflected off the surface

Normal: Imaginary line that is perpendicular to the surface at the point of incidence

Angle of Incidence: angle between the incident ray and the normal

Angle of Reflection: angle between the normal and the reflected ray

Laws of Reflection:

1) The incident ray, reflected ray, and the normal at the point of incidence all lie in the same plane

2) Angle of incidence = Angle of reflection

Differences between specular reflection and diffused reflection:

1) A specular reflection is all reflected in the same direction while a diffused reflection is reflected in different directions.

2) A specular reflection reflects on smooth surfaces while a diffused reflection reflects on rough surfaces.

3) A specular reflection results in a clear image formed while a diffused reflection results in a blur image formed.

Notes:

-All reflected rays and incident rays are to be drawn in solid lines, while working lines such as the normal is to be drawn in dotted lines.

-When drawing the reflected rays and incident rays, an arrowhead must be present to indicate the direction of a particularly light ray.

-Always use pencil to draw ray diagrams and protractor to ensure the normal is perpendicular to the surface

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Ray Diagram drawing for Reflection:

Every ray that is reflected off the mirror always follows the law of reflection (angle of incidence = angle of reflection). The image behind the mirror is virtual because light rays do not actually pass through the image and it could not be captured by a screen.

Steps for drawing ray diagram:

1) Draw a similar image in the mirror (Refer to the segment on image characteristics below to know the points to take note of when drawing images)

2) Draw 2 light rays from a point of the virtual image to the eye

3) Draw 2 solid light rays from the real object to the points of reflected rays on the mirror.

4) Draw the arrowheads to indicate the direction (Object -> mirror -> Observer)

Notes:

1) Always use ruler to measure the distance between the mirror and the object to ensure an accurate diagram

2) Use solid lines in front of the mirror and dotted lines behind the mirror and for working lines

Image characteristics of a Mirror

The image that we see on the mirror is formed when the light rays reflect off you, strike the mirror, and eventually travel to your eyes.

Characteristics of an image formed in plane mirror:

1) Same size as the object

2) Same distance behind the mirror as the object is in front of the mirror

3) Same orientation as the object, Ex, both the object and the image is upright

4) Laterally inverted

5) Virtual

Images formed in different types of mirror:

-Plane mirror:

Object position: Anywhere

Image position: on the opposite side of the mirror as the object/ same distance behind the mirror as the object is in front of it

Type of image: Virtual

Orientation of image: Same as object

Size of Image: Same as object

-Concave mirror:

Object position: Near mirror (inside focal point)

Image position: on the opposite side of the mirror as the object

Type of image: Virtual

Orientation of image: Same as object

Size of Image: Magnified

-Concave mirror:

Object position: Far from mirror (outside focal point)

Image position: same side of the mirror as the object

Type of image: real

Orientation of image: opposite of object

Size of Image: diminished

-Convex mirror:

Object position: Anywhere

Image position: on the opposite side of the mirror as the object

Type of image: Virtual

Orientation of image: Same as object

Size of Image: diminished

Sci Lesson 19/8

For today's lesson, we went through the online worksheet lenses, and the teacher had also clarify with us the important points to take note of when drawing lenses.
First of all, there must be 3 rays present. The 1st ray will be parallel to the principal axis and pass through the focal point on the other side. The second ray will pass through the optical centre and go straight in that direction. Last but not least, the third ray will pass through the focal point and be parallel to the princpal axis on the other side. We had also learnt the different terms that will award us marks when answering questions regarding ray diagram for lenses, for example optical centre, principal axis, focal point, focal length and focal plane.
We had also learnt about the difference between long lenses and short lenses. For example, the image obtained from long lenses is diminished, inverted and real, whereas the image obtained form short lenses is magnified, upright and virtual. Today, I had learnt more on the topic lenses, and also went through some of the lenses questions. Through the questions, I had roughly know what will be the type of questions that will normally come out for lenses. Our teacher had also emphasis on us the importance of the terms when answering and also the drawing of ray diagrams.

Sci Lesson 15/8

Today, we had gone through practical 14, 15, and 16, which mainly covered lenses and lights. Before this lesson, I had actually read up on lenses and lights. However, I was just memorizing the facts and concepts, without really understanding it. After today’s demonstration and experiment by the teacher, I had seen for my own eyes and I had definitely understood more.

I had seen for myself when the lens had converged upon convex lens, and diverged upon concave lens. The teacher had also explained that the more curved the sides are, the shorter the focal length (the length measured from the screen /meeting point of the rays to the lens) will be. We had also done the experiment with prisms and we had made use of the prism to show that reflected rays and emergent rays can only be parallel when the surfaces they enter/leave are parallel too, such as using 2 prisms. Last but not least, we had also learnt about identifying which color of light bend the most/least and whether it travels the fastest/slowest. Apparently, the light ray that reveal the more color bends the most and is the slowest, and vice-versa.

Reflection on Term 3 test

Today we had gone through our science Term 3 test. I had gotten a decent grade and I’m satisfied with it. We had also went through the science test’s answer today and I realised some of the mistakes are mistakes that I should not have made in the test.

After looking at my test paper, I realized that I’m better at theory question, where the question is asking me on my concept and knowledge. I am also quite good in applying these concepts into application questions, such as describing the effects of the food chains etc. However, I am weak at drawing questions, especially when they told us to draw reflected and refracted rays. I find it quite hard to understand exactly what did the question demand for. However, I think the only way to counter this weakness of mine is to practice more. As I practice more, I will get used to the questions and also the type of questions that will normally come out on the test itself. Overall, I am quite satisfied with my results and I hoped to achieve the same result, if not better, for my next test.

Sci Lesson 1/8

Today, our teacher went through the reflection assignment 1 with us and also a quick recap on ecology and nutrient cycle for this Friday test. Though it was just a quick recap, it was really useful. I had been reminded a lot about ecology today, and I’m glad for this recap lesson today.

Some of the things that I had been reminded were to never ever include man in the food chain. The teacher had also remind us that we need not know examples that were out of our syllables, for example plants that we never heard before, as long as we had general knowledge of the different plants in different habitats will be fine. Such examples will be cactus in a dry environment and an orchid in an environment where the temperature is lower. Lastly, our teacher also reminded us the importance of keywords and phrases in our answers, phrases such as “angle of incidence equals to angle of reflection”.

After today’s recap lesson, I am more confident for the test. My questions were raised today too and I believe after this recap lesson, it would definitely assist our class overall results too. I really hope there would be such a similar recap lesson in future tests.