Grade 8 Natural Science - Light and the Solar System

Flashcards testing core natural science concepts including optics, reflection, refraction, visible spectrum, pinhole cameras, and planetary characteristics of the solar system.

What is the Law of Reflection?

The Law of Reflection states that the angle of incidence is equal to the angle of reflection ($\text{Angle of incidence} = \text{Angle of reflection}$).

From where are the angle of incidence and angle of reflection measured in a reflection diagram?

Angles are always measured between the respective rays and the normal, which is an imaginary line perpendicular (90^\n\circ) to the surface.

What is diffuse reflection and when does it occur?

Diffuse reflection occurs when light hits an uneven or rough surface, causing the light rays to reflect in many different directions and scatter.

How does light bend when entering a denser medium like glass from air?

When light passes from a less dense medium (air) into a denser medium (glass), it refracts towards the normal.

How does light bend when exiting a denser medium like glass into air?

When light passes from a denser medium (glass) into a less dense medium (air), it refracts away from the normal.

What mnemonic acronym is used to remember the seven colours of the visible spectrum?

ROYGBIV, standing for Red, Orange, Yellow, Green, Blue, Indigo, and Violet.

What is light dispersion?

Dispersion is the process where white light is refracted and separated into its different spectral colours.

Which spectral colour of light has the most energy, highest frequency, shortest wavelength, and refracts the most?

Violet light.

Which spectral colour of light has the least energy, lowest frequency, longest wavelength, and refracts the least?

Red light.

Why do red sunsets occur?

Red sunsets occur because red light is refracted the least, while other colours are scattered away, leaving red visible.

What key properties characterize the image formed by a pinhole camera?

The image formed by a pinhole camera is real and inverted (upside-down).

How does changing the size of the hole affect a pinhole camera image?

A bigger hole produces a brighter but less sharp image, while a smaller hole produces a dimmer but sharply outlined image.

What happens to the projected image size in a pinhole camera when the camera is moved further from the object?

Moving the camera further from the object makes the image on the film larger.

What is the difference between luminous and non-luminous objects?

Luminous objects produce and emit their own light energy (e.g., the Sun, stars), whereas non-luminous objects do not produce light and are seen by reflecting light from a luminous source (e.g., the Moon, planets).

How do transparent, translucent, and opaque substances differ?

Transparent substances allow most light through so objects are clearly visible; translucent substances allow some light through but objects cannot be seen clearly; opaque substances allow no light through and create shadows.

What is the primary process that generates energy in the Sun?

Nuclear fusion, where hydrogen gas is converted into helium gas.

What are the core, surface, and sunspot temperatures of the Sun in Kelvin?

The Sun's core temperature is $15.6\,\text{million K}$, its surface temperature is $5800\,\text{K}$, and sunspot temperatures average $3800\,\text{K}$.

What is the approximate elemental composition of the Sun?

The Sun is composed of approximately $74.5\%$ hydrogen, $24.5\%$ helium, and $1\%$ other substances (metals).

How much hydrogen is converted into helium in the Sun every second?

Every second, $700,000,000\,\text{tons}$ of hydrogen is converted into $695,000,000\,\text{tons}$ of helium.

What three criteria must an object meet to be classified as a planet?

1. It must revolve around the Sun. 2. It must have enough mass for gravity to pull it into a nearly round shape. 3. It must have cleared its orbit of other debris.

What is the correct order of the eight planets starting from the closest to the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

What are the key facts regarding Mercury's composition, temperature range, and orbital period?

Mercury is a dense iron-rich planet with no moons located $58\,\text{million km}$ from the Sun, featuring extreme temperatures from $430\,^\circ\text{C}$ to $-180\,^\circ\text{C}$, an orbital period of $88\,\text{days}$, and a rotation period of $59\,\text{days}$.

Why is Venus the hottest planet in the solar system, and what is its average temperature?

Venus has a thick atmosphere predominantly made of carbon dioxide and lacks an ozone layer, resulting in extreme heat retention with an average surface temperature of $467\,^\circ\text{C}$.

What is Earth's orbital period and orbital speed around the Sun?

Earth orbits the Sun in $365.25\,\text{days}$ at a speed of $30\,\text{km}\cdot\text{s}^{-1}$.

What are the names of Mars's two moons and its rotation period?

Mars has two moons named Deimos and Phobos, and it rotates on its axis in $24.6\,\text{hours}$.

What are the main characteristics of Jupiter regarding size, rotation, and moon count?

Jupiter is the largest planet (over 1,300 Earths in volume), a gas giant featuring the Great Red Spot storm, has the fastest rotation at $9.8\,\text{hours}$, orbits in $4,332\,\text{days}$, and has 63 moons.

What elements primarily make up Saturn, and what makes it unique among planets?

Saturn is a gas giant primarily made of hydrogen and helium (the two lightest elements), making it the lightest planet, and it is famous for its prominent ring system and 53 moons.