This is the example image i have taken this few days.
why can't I get the full white background like the photo from the internet?
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The short answer: You need more light on the background so that you can intentionally blow it out without blowing out the product. Then expose so that the background is on the verge of blowing out. In post-processing push the exposure for the highlights up until the background is pure white.
This has been covered many times here in the past:
How do I improve the results of photos taken in a light-box?
Why hasn't buying powerful lights improved my lightbox images?
How do I properly do shadowless product photos?
Why can't I get a decent white background with product photography?