Đề ôn thi Đề thi vào lớp 10 Trường Phổ thông Năng khiếu môn Tiếng Anh - Mã đề PTNK-102

When we discuss distances on Earth, we use units like kilometers. However, when we look at the night sky, the distances to stars are so immense that these units become impractical. To manage these huge numbers, astronomers use a special unit of measurement. The term ‘light-year’ (21) __________ to express these cosmic distances. Despite its name, it is important to remember that a light-year is a unit of distance, not time.

A light-year is defined as the total distance that light travels in one year. The principle behind this measurement is that the speed of light is constant and the fastest possible speed in the universe. Light travels through the vacuum of space at a phenomenal speed of approximately 300,000 kilometers per second. This consistency provides a reliable ruler for the cosmos.

Multiplying this speed by the seconds in a year results in an astonishing figure. Therefore, one light-year is equal to about 9.46 trillion kilometers. This calculation shows that even a journey of a few light-years covers a truly (22) __________ distance, one that is difficult for the human mind to comprehend fully.

This unit helps (23) __________ sense of cosmic geography. For example, Proxima Centauri, the nearest star to our Sun, is about 4.2 light-years away. The Andromeda Galaxy, a neighboring galaxy (24) __________ is visible on a clear night, is about 2.5 million light-years from us. This means the light we see from it today started its journey 2.5 million years ago.

In conclusion, the light-year is an essential concept in astronomy. Without it, there would be no practical way to chart the vast expanses between celestial bodies or to comprehend their scale. It simplifies cosmic calculations and gives us a way to look back in time, making it one of the most important tools for any serious astronomer.

In today's digital world, apps like Instagram and TikTok are almost always at our fingertips. Every time we scroll, we're bombarded with countless images – seemingly perfect faces, sculpted bodies, and idealized lives. While these platforms offer entertainment, they can also subtly shape how we view ourselves. [I] For many teenagers, this constant exposure to what appears to be flawless beauty can lead to a challenging journey with their own body image, making it harder to feel truly good. It’s crucial to understand that what glitters online often isn't real.

The issue isn't just seeing beautiful people; it's the unrealistic standards these platforms promote. Many "perfect" images are heavily filtered, strategically posed, or professionally edited to remove perceived flaws. Influencers and celebrities often have teams perfecting their online presence. [II] The pressure to achieve this manufactured ideal can be immense.

This global phenomenon has particular resonance in countries like Vietnam. Here, the influence of K-Pop idols and social media personalities sets a very specific, often extremely thin or highly stylized, beauty standard. Young Vietnamese people constantly see images promoting specific skin tones, facial features, and body shapes far from their natural or healthy form. [III] This creates cultural pressure, amplifying dissatisfaction and inadequacy if they don't fit these narrow, unattainable molds. The desire to emulate these idols can overshadow genuine self-acceptance.

When you’re a teenager, seeing these "perfect" bodies and faces on your phone screen every day can be incredibly draining. It's easy to fall into the trap of constant comparison, looking at your own reflection and finding flaws that weren't there before. [IV] This comparison can erode your self-esteem, leading to anxiety and body dissatisfaction. It's vital to remember that these images are rarely a true reflection of reality; they are often carefully constructed illusions designed to capture attention, not to represent real life or healthy bodies.

Instead of striving for an edited version of perfection, focus on what truly matters: your own health, strength, and overall well-being. Your body is unique and incredible, capable of amazing things. Learn to appreciate its capabilities rather than its appearance compared to others. Be critical of online content; unfollow accounts that make you feel bad, and seek out diverse, body-positive content that celebrates all shapes and sizes. Feeling good about yourself starts with accepting and loving the real you, not a filtered fantasy.