Latihan TOEFL Listening 19: Lecture: The Doppler Effect and Redshift
Ini transkrip percakapan atau kuliah untuk latihan listening. Coba pahami isinya, lalu jawab 10 soal di bawah.
Most people have experienced the Doppler effect without necessarily knowing its name: the pitch of a passing ambulance siren sounds higher as it approaches and lower as it moves away, even though the siren itself never changes frequency. This occurs because sound waves become compressed in front of a moving source and stretched out behind it, altering the frequency perceived by a stationary listener.
The same underlying principle applies to light, though the effect is generally far more subtle at everyday speeds. When a light-emitting object moves away from an observer, its light waves stretch, shifting the observed light toward longer, redder wavelengths, a phenomenon known as redshift; conversely, an object moving toward the observer produces blueshift, a shift toward shorter wavelengths.
Astronomers rely heavily on this principle to study the universe. By measuring the redshift of light from distant galaxies, Edwin Hubble demonstrated in the 1920s that most galaxies are moving away from us, with more distant galaxies receding faster, providing crucial early evidence that the universe is expanding. Today, precise redshift measurements remain fundamental to modern cosmology, allowing astronomers to estimate cosmic distances and trace the universe's expansion history with remarkable precision.
Soal
1. What is the main purpose of this lecture?
- Describing how ambulance sirens are manufactured
- Explaining the Doppler effect and its application to studying the universe's expansion
- Arguing that the universe is not actually expanding
- Comparing sound waves and radio waves in detail
Lihat jawaban dan pembahasan
Jawaban: B. Explaining the Doppler effect and its application to studying the universe's expansion
Lecture menjelaskan efek Doppler untuk suara lalu penerapannya pada cahaya dan kosmologi.
2. According to the lecture, why does an ambulance siren sound higher as it approaches?
- The siren's actual frequency increases as it approaches
- The listener's hearing temporarily improves
- The siren is turned up louder as it approaches
- Sound waves become compressed in front of the moving source
Lihat jawaban dan pembahasan
Jawaban: D. Sound waves become compressed in front of the moving source
Disebutkan eksplisit alasan ini di paragraf 1.
3. According to the lecture, what is redshift?
- A change in the color of an object regardless of its motion
- A shift of light toward shorter wavelengths as an object moves away
- A type of sound wave phenomenon only
- A shift of light toward longer, redder wavelengths as an object moves away
Lihat jawaban dan pembahasan
Jawaban: D. A shift of light toward longer, redder wavelengths as an object moves away
Ini definisi langsung yang diberikan di paragraf 2.
4. It can be inferred that an object producing blueshift is
- Moving away from the observer
- Moving toward the observer
- Not moving at all
- Too far away to be observed
Lihat jawaban dan pembahasan
Jawaban: B. Moving toward the observer
Disebutkan blueshift terjadi pada objek 'moving toward the observer'.
5. Why does the lecturer mention Edwin Hubble?
- To credit the astronomer who used redshift to demonstrate the universe's expansion
- To argue that Hubble's findings have since been disproven
- To describe Hubble's early life in detail
- To compare Hubble with other unrelated scientists
Lihat jawaban dan pembahasan
Jawaban: A. To credit the astronomer who used redshift to demonstrate the universe's expansion
Hubble disebut sebagai orang yang membuktikan alam semesta mengembang menggunakan pengukuran redshift.
6. The word 'receding' as used in the lecture is closest in meaning to
- Remaining perfectly still
- Rotating in place
- Moving away or retreating
- Moving closer or approaching
Lihat jawaban dan pembahasan
Jawaban: C. Moving away or retreating
'Receding faster' berarti menjauh dengan kecepatan lebih tinggi.
7. According to the lecture, what did Hubble find about the relationship between galaxy distance and speed?
- More distant galaxies are receding faster
- All galaxies move at exactly the same speed
- More distant galaxies are approaching faster
- Distance has no relationship to galaxy speed
Lihat jawaban dan pembahasan
Jawaban: A. More distant galaxies are receding faster
Disebutkan eksplisit temuan ini di paragraf 3.
8. It can be inferred that the Doppler effect for light at everyday speeds is
- Always more noticeable than the effect for sound
- Completely undetectable under any circumstances
- Only observable using sound equipment
- Generally more subtle and harder to notice than the effect for sound
Lihat jawaban dan pembahasan
Jawaban: D. Generally more subtle and harder to notice than the effect for sound
Disebutkan eksplisit efeknya 'far more subtle at everyday speeds' dibanding efek untuk suara.
9. According to the lecture, what do astronomers use redshift measurements for today?
- Estimating cosmic distances and tracing the universe's expansion history
- Only measuring the speed of sound
- Only predicting weather patterns
- Only designing spacecraft engines
Lihat jawaban dan pembahasan
Jawaban: A. Estimating cosmic distances and tracing the universe's expansion history
Disebutkan eksplisit penggunaan modern ini di kalimat terakhir.
10. Why does the lecturer begin with the ambulance siren example?
- To introduce the Doppler effect using a familiar, everyday experience before applying it to light
- To criticize modern ambulance siren designs
- To explain how sirens are used in emergency response
- To argue that sound and light behave in completely unrelated ways
Lihat jawaban dan pembahasan
Jawaban: A. To introduce the Doppler effect using a familiar, everyday experience before applying it to light
Contoh sirene ambulans dipakai sebagai pengantar yang familiar sebelum masuk ke penerapannya pada cahaya.