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Explain why the menstrual cycle stops during pregnancy.
The menstrual cycle stops during pregnancy because the fertilized embryo implants directly into the inner uterine wall. To nourish and support embryonic development, the body secretes continuous hormones that keep the blood-rich uterine lining intact instead of breaking down. Because ovulation and tRead more
The menstrual cycle stops during pregnancy because the fertilized embryo implants directly into the inner uterine wall. To nourish and support embryonic development, the body secretes continuous hormones that keep the blood-rich uterine lining intact instead of breaking down. Because ovulation and the shedding of the uterine lining are suppressed, menstruation temporarily ceases until after childbirth.
For more NCERT Solutions of Class 9 Science Exploration Chapter 11 Reproduction How Life Continues Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-11/
See lessWhy are flowers that bloom at night white or light in colour as compared to flowers that bloom during the day?
Night-blooming flowers are pollinated primarily by nocturnal insects, such as moths and beetles, which navigate in low light. Bright daytime colors like red or purple are invisible in the dark. White or pale petals reflect the available moonlight effectively, making the blossoms stand out against daRead more
Night-blooming flowers are pollinated primarily by nocturnal insects, such as moths and beetles, which navigate in low light. Bright daytime colors like red or purple are invisible in the dark. White or pale petals reflect the available moonlight effectively, making the blossoms stand out against dark foliage and guiding nocturnal pollinators directly to their nectar.
For more NCERT Solutions of Class 9 Science Exploration Chapter 11 Reproduction How Life Continues Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-11/
See lessWhich observation best supports the idea that sound is a mechanical wave? (i) Sound shows reflection (ii) Sound needs a medium to propagate (iii) Sound has frequency (iv) Sound carries energy
The correct option is (ii) Sound needs a medium to propagate. By definition, mechanical waves propagate through the physical displacement and periodic collisions of particles within a material medium. Because sound waves cannot travel across a vacuum, as demonstrated when air is evacuated from a belRead more
The correct option is (ii) Sound needs a medium to propagate. By definition, mechanical waves propagate through the physical displacement and periodic collisions of particles within a material medium. Because sound waves cannot travel across a vacuum, as demonstrated when air is evacuated from a bell jar, their strict dependence on a material medium confirms their mechanical nature.
For more NCERT Solutions of Class 9 Science Exploration Chapter 10 Sound Waves Characteristics and Applications Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-10/
See lessFor a sound wave propagating in a medium, increasing its frequency will increase its (i) wavelength (ii) speed (iii) number of compressions per second (iv) time period
The correct option is (iii) number of compressions per second. Frequency is defined as the number of complete density oscillations or compressions passing a given location per unit time. Since wave speed remains constant in a uniform medium, raising the frequency decreases both the wavelength and thRead more
The correct option is (iii) number of compressions per second. Frequency is defined as the number of complete density oscillations or compressions passing a given location per unit time. Since wave speed remains constant in a uniform medium, raising the frequency decreases both the wavelength and the time period, directly increasing the number of compressions produced each second.
For more NCERT Solutions of Class 9 Science Exploration Chapter 10 Sound Waves Characteristics and Applications Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-10/
See lessIf 20 compressions pass a point in 4 seconds, the frequency is (i) 80 Hz (ii) 5 Hz (iii) 10 Hz (iv) 0.2 Hz
The correct option is (ii) 5 Hz. The frequency of a periodic wave is calculated by dividing the total number of complete oscillations or passing compressions by the total time taken. Here, dividing 20 compressions by 4 seconds gives 5 oscillations per second. Since one cycle per second equals one heRead more
The correct option is (ii) 5 Hz. The frequency of a periodic wave is calculated by dividing the total number of complete oscillations or passing compressions by the total time taken. Here, dividing 20 compressions by 4 seconds gives 5 oscillations per second. Since one cycle per second equals one hertz, the wave frequency is 5 Hz.
For more NCERT Solutions of Class 9 Science Exploration Chapter 10 Sound Waves Characteristics and Applications Question Answer (2026-27)
https://www.tiwariacademy.com/ncert-solutions/class-9/science/exploration-chapter-10/
See less