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These two short online tutorials discuss how the earth rotates and then the earth's revolutions.

In the first URL, the YouTube video explains why earth has spring, summer, autumn and winter seasons. The second URL summarizes the key takeaway points.

There are many different processes and phenomena that emit electromagnetic radiation. Humans have taken advantage of many of these processes to develop technologies that use electromagnetic radiation.

The beauty of a coral reef, the warm radiance of sunshine, the sting of sunburn, the X-ray revealing a broken bone, even microwave popcorn—all are brought to us by electromagnetic waves. The list of the various types of electromagnetic waves, ranging from radio transmission waves to nuclear gamma-ray (γ-ray) emissions, is interesting in itself.

Even more intriguing is that all of these different phenomena are manifestations of the same thing—electromagnetic waves (see Figure 15.1). What are electromagnetic waves? How are they created, and how do they travel? How can we understand their widely varying properties? What is the relationship between electric and magnetic effects? These and other questions will be explored.

An image that illustrates light reflecting off a plain mirror.

Photoelectric materials emit electrons when they absorb light of a high-enough frequency.

Outcomes

By the end of this course you will:

• Be able to define the 'reflection of light'
• Understand the difference between reflected and incident rays
• Be familiar with the two types of reflection viz.: regular and irregular reflection
• Have an understanding of the laws of reflection

This YouTube video elaborates on what weather is and what causes changes in the weather.